Skip to Main Navigation
Skip to Page Content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Share This:
https://ntp.niehs.nih.gov/go/4546

TDMS Study 05185-03 Pathology Tables


                                     INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)
                                                       ISOBUTYL NITRITE (IBN)


NTP Experiment-Test: 05185-03                                                                                     Report: PEIRPT03
Study Type: CHRONIC                                                                                               Date: 05/20/95
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26




       Facility:  I. I. T. Research Institute

       Chemical CAS #:  542-56-3

       Lock Date:  05/22/92

       Cage Range:  All

       Reasons For Removal:    All

       Removal Date Range:     All

       Treatment Groups:       Include All
































a  Number of animals examined microscopically at site and number of animals with lesion

                                                             Page   1

NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          56           56           56           56                                     
  Scheduled Sacrifice                                 10           10           10           10                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                13            4            7            6                                     
    Natural Death                                      4            6            8            7                                     
  Survivors                                                                                                                         
    Terminal Sacrifice                                29           35           30           33                                     
    Natural Death                                                                1                                                  
  Missing                                                           1                                                               
  Animals Examined Microscopically                    56           55           56           56                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Intestine Large, Colon                             (56)         (54)         (54)         (54)                                   
      Abscess                                                                                 1 (2%)                                
   Intestine Large, Cecum                             (56)         (54)         (53)         (53)                                   
      Inflammation                                     1 (2%)                                                                       
      Necrosis                                         1 (2%)                                                                       
   Intestine Small, Ileum                             (54)         (51)         (50)         (51)                                   
      Inflammation                                     1 (2%)                                                                       
   Liver                                              (56)         (54)         (56)         (56)                                   
      Angiectasis                                                   1 (2%)       2 (4%)                                             
      Basophilic Focus                                 7 (13%)      6 (11%)     15 (27%)      7 (13%)                               
      Basophilic Focus, Multiple                      22 (39%)     34 (63%)     30 (54%)     40 (71%)                               
      Clear Cell Focus                                 3 (5%)       1 (2%)       2 (4%)       2 (4%)                                
      Clear Cell Focus, Multiple                                                 1 (2%)       1 (2%)                                
      Congestion                                       1 (2%)                    3 (5%)       4 (7%)                                
      Developmental Malformation                       2 (4%)                                 2 (4%)                                
      Eosinophilic Focus                               1 (2%)       8 (15%)      5 (9%)       2 (4%)                                
      Eosinophilic Focus, Multiple                                               3 (5%)       1 (2%)                                
      Fatty Change                                    10 (18%)      4 (7%)       9 (16%)      4 (7%)                                
      Hematopoietic Cell Proliferation                 4 (7%)                                                                       
      Hemorrhage                                       1 (2%)                                 1 (2%)                                
      Hepatodiaphragmatic Nodule                       3 (5%)       3 (6%)       5 (9%)       6 (11%)                               
      Infiltration Cellular, Lymphocyte                             1 (2%)       1 (2%)       1 (2%)                                
      Inflammation                                     4 (7%)       3 (6%)       6 (11%)      2 (4%)                                
      Mixed Cell Focus                                 2 (4%)                    2 (4%)                                             
      Necrosis                                         3 (5%)       1 (2%)       1 (2%)       3 (5%)                                
      Pigmentation                                                               1 (2%)       1 (2%)                                
      Vacuolization Cytoplasmic                                                  4 (7%)                                             
      Centrilobular, Cytoplasmic Alteration                                      1 (2%)                                             
   Mesentery                                          (1)                       (4)          (2)                                    
      Fat, Necrosis                                    1 (100%)                  4 (100%)     2 (100%)                              
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    2                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
   Pancreas                                           (56)         (55)         (56)         (56)                                   
      Accessory Spleen                                 1 (2%)                    1 (2%)                                             
      Ectopic Liver                                                                           2 (4%)                                
      Infiltration Cellular, Lymphocyte                             1 (2%)                                                          
      Acinar Cell, Atrophy                            19 (34%)     28 (51%)     26 (46%)     25 (45%)                               
   Salivary Glands                                    (56)         (55)         (55)         (56)                                   
      Inflammation                                                  1 (2%)                                                          
   Stomach, Forestomach                               (56)         (55)         (56)         (56)                                   
      Hyperplasia                                      2 (4%)                    3 (5%)       1 (2%)                                
      Inflammation                                                  1 (2%)       1 (2%)       1 (2%)                                
      Ulcer                                            3 (5%)                    2 (4%)                                             
      Ulcer, Multiple                                  2 (4%)                    1 (2%)                                             
   Stomach, Glandular                                 (56)         (54)         (55)         (56)                                   
      Inflammation                                     1 (2%)                    1 (2%)                                             
      Ulcer                                            2 (4%)                                 1 (2%)                                
      Ulcer, Multiple                                  1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (56)         (55)         (56)         (56)                                   
      Cardiomyopathy                                  38 (68%)     30 (55%)     34 (61%)     41 (73%)                               
      Atrium, Thrombosis                               2 (4%)                                 2 (4%)                                
      Endocardium, Proliferation                                                              1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (56)         (55)         (56)         (56)                                   
      Angiectasis                                      4 (7%)       7 (13%)     10 (18%)     10 (18%)                               
      Congestion                                                                 1 (2%)       1 (2%)                                
      Cyst                                             1 (2%)                                                                       
      Cytoplasmic Alteration                                        1 (2%)                                                          
      Degeneration                                     1 (2%)       2 (4%)       1 (2%)       1 (2%)                                
      Hemorrhage                                       1 (2%)       1 (2%)       1 (2%)       4 (7%)                                
      Hyperplasia                                      5 (9%)       5 (9%)                    3 (5%)                                
      Hypertrophy                                      1 (2%)       1 (2%)       1 (2%)       1 (2%)                                
      Infiltration Cellular, Lymphocyte                                                       1 (2%)                                
      Necrosis                                         1 (2%)                                                                       
      Vacuolization Cytoplasmic                        8 (14%)     13 (24%)      6 (11%)     10 (18%)                               
   Adrenal Medulla                                    (55)         (55)         (55)         (56)                                   
      Angiectasis                                      1 (2%)                                                                       
      Hyperplasia                                      2 (4%)       4 (7%)       3 (5%)       5 (9%)                                
   Pituitary Gland                                    (56)         (53)         (55)         (56)                                   
      Angiectasis                                                                             1 (2%)                                
      Congestion                                                                              1 (2%)                                
      Cyst                                             3 (5%)                    1 (2%)                                             
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    3                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ENDOCRINE SYSTEM - CONT                                                                                                             
      Hyperplasia                                      1 (2%)                                                                       
      Pars Distalis, Angiectasis                      11 (20%)     12 (23%)      5 (9%)       7 (13%)                               
      Pars Distalis, Cyst                             16 (29%)     21 (40%)     13 (24%)      9 (16%)                               
      Pars Distalis, Hyperplasia                       9 (16%)     24 (45%)     15 (27%)     21 (38%)                               
      Pars Nervosa, Developmental Malformation                      1 (2%)                                                          
   Thyroid Gland                                      (56)         (55)         (56)         (56)                                   
      C-Cell, Hyperplasia                              8 (14%)      4 (7%)       5 (9%)       6 (11%)                               
      Follicle, Dilatation                             1 (2%)                    1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   Tissue NOS                                                      (1)                                                              
      Developmental Malformation                                    1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Clitoral Gland                                     (54)         (54)         (54)         (56)                                   
      Abscess                                                       1 (2%)       1 (2%)                                             
      Ectasia                                         32 (59%)     33 (61%)     38 (70%)     37 (66%)                               
      Hyperplasia                                      2 (4%)       4 (7%)       1 (2%)       6 (11%)                               
      Inflammation                                     2 (4%)       3 (6%)       5 (9%)       2 (4%)                                
   Ovary                                              (56)         (55)         (56)         (56)                                   
      Cyst                                             5 (9%)       9 (16%)      2 (4%)       2 (4%)                                
      Hemorrhage                                                                 1 (2%)                                             
      Bilateral, Cyst                                               1 (2%)       1 (2%)                                             
      Corpus Luteum, Hyperplasia                       1 (2%)                                                                       
   Uterus                                             (56)         (55)         (56)         (56)                                   
      Angiectasis                                                                             1 (2%)                                
      Cyst                                                          1 (2%)                    2 (4%)                                
      Dilatation                                       1 (2%)       2 (4%)       5 (9%)       2 (4%)                                
      Hemorrhage                                       1 (2%)                                                                       
      Prolapse                                                                   1 (2%)                                             
      Bilateral, Dilatation                            2 (4%)                                                                       
      Endometrium, Hyperplasia                         1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (56)         (55)         (56)         (56)                                   
      Atrophy                                                                    2 (4%)                                             
      Hyperplasia                                      7 (13%)      7 (13%)      6 (11%)      6 (11%)                               
      Myelofibrosis                                                 1 (2%)       1 (2%)       2 (4%)                                
   Lymph Node                                         (1)          (1)                       (3)                                    
      Axillary, Hyperplasia, Lymphoid                               1 (100%)                  1 (33%)                               
      Axillary, Hyperplasia, Plasma Cell                            1 (100%)                                                        
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    4                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - CONT                                                                                                         
      Lumbar, Cyst                                     1 (100%)                                                                     
      Lumbar, Hyperplasia, Lymphoid                    1 (100%)                                                                     
      Lumbar, Pigmentation                             1 (100%)                               1 (33%)                               
   Lymph Node, Bronchial                              (36)         (40)         (46)         (38)                                   
      Hemorrhage                                      12 (33%)     23 (58%)     22 (48%)     20 (53%)                               
      Pigmentation                                     2 (6%)       7 (18%)      9 (20%)      7 (18%)                               
   Lymph Node, Mandibular                             (55)         (55)         (53)         (53)                                   
      Cyst                                                          1 (2%)                                                          
      Hemorrhage                                       2 (4%)       1 (2%)       2 (4%)       1 (2%)                                
      Hyperplasia, Lymphoid                                         1 (2%)       1 (2%)                                             
      Hyperplasia, Plasma Cell                         2 (4%)       3 (5%)                    1 (2%)                                
      Pigmentation                                                               2 (4%)                                             
   Lymph Node, Mesenteric                             (56)         (55)         (56)         (55)                                   
      Edema                                            1 (2%)                                                                       
      Hemorrhage                                       8 (14%)      8 (15%)      8 (14%)      8 (15%)                               
      Pigmentation                                     1 (2%)                                 1 (2%)                                
   Lymph Node, Mediastinal                            (54)         (54)         (51)         (53)                                   
      Hemorrhage                                      37 (69%)     41 (76%)     41 (80%)     35 (66%)                               
      Infiltration Cellular, Histiocyte                1 (2%)                                                                       
      Pigmentation                                    22 (41%)     31 (57%)     31 (61%)     17 (32%)                               
   Spleen                                             (56)         (55)         (54)         (56)                                   
      Congestion                                                                              1 (2%)                                
      Developmental Malformation                                                              1 (2%)                                
      Hematopoietic Cell Proliferation                 5 (9%)      11 (20%)      7 (13%)     10 (18%)                               
      Pigmentation                                     1 (2%)                    3 (6%)       3 (5%)                                
   Thymus                                             (54)         (53)         (55)         (54)                                   
      Atrophy                                         44 (81%)     26 (49%)     34 (62%)     24 (44%)                               
      Congestion                                                                 1 (2%)       1 (2%)                                
      Cyst                                                                                    1 (2%)                                
      Hemorrhage                                                    2 (4%)       4 (7%)       7 (13%)                               
      Necrosis                                                                   1 (2%)                                             
      Pigmentation                                     1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (56)         (55)         (56)         (56)                                   
      Abscess                                                       1 (2%)                                                          
      Galactocele                                                                             1 (2%)                                
      Hemorrhage                                                    1 (2%)                                                          
      Hyperplasia                                                                             1 (2%)                                
      Inflammation                                                                            2 (4%)                                
      Lactation                                       17 (30%)      7 (13%)      9 (16%)      8 (14%)                               
   Skin                                               (56)         (55)         (56)         (56)                                   
      Abscess                                                                                 1 (2%)                                
      Ulcer                                                         1 (2%)                                                          
      Ulcer, Multiple                                               1 (2%)                                                          
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    5                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
INTEGUMENTARY SYSTEM - CONT                                                                                                         
      Tail, Hyperkeratosis                             1 (2%)                                                                       
      Tail, Parakeratosis                              1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (56)         (55)         (56)         (56)                                   
      Femur, Hyperostosis                                           6 (11%)      2 (4%)       5 (9%)                                
      Turbinate, Hyperostosis                                       3 (5%)       2 (4%)       2 (4%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (56)         (55)         (56)         (56)                                   
      Compression                                     13 (23%)      8 (15%)     15 (27%)     10 (18%)                               
      Cyst                                                                                    1 (2%)                                
      Hemorrhage                                       2 (4%)                    5 (9%)       2 (4%)                                
      Hydrocephalus                                    3 (5%)                    1 (2%)       1 (2%)                                
      Necrosis                                                                   3 (5%)                                             
      Thrombosis                                       1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (56)         (55)         (56)         (56)                                   
      Foreign Body                                                                            1 (2%)                                
      Hemorrhage                                                                 1 (2%)                                             
      Infiltration Cellular, Lymphocyte                                                       3 (5%)                                
      Inflammation                                     3 (5%)                    4 (7%)       6 (11%)                               
      Metaplasia, Squamous                                                                    1 (2%)                                
      Epithelium, Hyperplasia                                                    2 (4%)       2 (4%)                                
   Lung                                               (56)         (55)         (56)         (56)                                   
      Congestion                                                    4 (7%)       6 (11%)      2 (4%)                                
      Hemorrhage                                      10 (18%)     15 (27%)     10 (18%)      9 (16%)                               
      Infiltration Cellular, Histiocyte                1 (2%)       1 (2%)       1 (2%)       2 (4%)                                
      Inflammation                                     4 (7%)       4 (7%)       3 (5%)       3 (5%)                                
      Alveolar Epithelium, Hyperplasia                 4 (7%)      12 (22%)     12 (21%)     35 (63%)                               
   Nose                                               (56)         (55)         (55)         (56)                                   
      Angiectasis                                                   1 (2%)       3 (5%)       1 (2%)                                
      Foreign Body                                     2 (4%)       1 (2%)                    1 (2%)                                
      Hemorrhage                                                    1 (2%)                    1 (2%)                                
      Inflammation                                     7 (13%)      5 (9%)       4 (7%)       7 (13%)                               
      Goblet Cell, Hyperplasia                         1 (2%)       4 (7%)       2 (4%)       3 (5%)                                
      Nasolacrimal Duct, Inflammation                  2 (4%)       2 (4%)                    2 (4%)                                
      Olfactory Epithelium, Cytoplasmic Alteration     2 (4%)                    3 (5%)       9 (16%)                               
      Respiratory Epithelium, Hyperplasia              3 (5%)       2 (4%)                    2 (4%)                                
   Trachea                                            (56)         (55)         (56)         (56)                                   
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    6                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS FEMALE                   CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
RESPIRATORY SYSTEM - CONT                                                                                                           
      Inflammation                                                  1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                             (1)          (1)                                                 
      Hemorrhage                                                    1 (100%)                                                        
      Bilateral, Lens, Cataract                                                  1 (100%)                                           
      Lens, Cataract                                                1 (100%)                                                        
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (56)         (55)         (56)         (56)                                   
      Angiectasis                                                                1 (2%)                                             
      Congestion                                                    1 (2%)       1 (2%)       1 (2%)                                
      Cyst                                             1 (2%)                                                                       
      Hypoplasia                                                    1 (2%)                                                          
      Infarct                                          1 (2%)                                                                       
      Mineralization                                  14 (25%)     16 (29%)     15 (27%)     17 (30%)                               
      Necrosis                                                                   1 (2%)                                             
      Nephropathy, Chronic                            52 (93%)     44 (80%)     43 (77%)     44 (79%)                               
      Pigmentation                                     3 (5%)                    4 (7%)       1 (2%)                                
      Transitional Epithelium, Hyperplasia             1 (2%)                                                                       
   Urinary Bladder                                    (56)         (54)         (55)         (52)                                   
      Dilatation                                       1 (2%)                    1 (2%)                                             
      Infiltration Cellular, Lymphocyte                             1 (2%)                                                          
      Arteriole, Inflammation                                                                 1 (2%)                                
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    7                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
DISPOSITION SUMMARY                                                                                                                 
  Animals Initially In Study                          56           56           56           56                                     
  Scheduled Sacrifice                                 10           10           10           10                                     
  Early Deaths                                                                                                                      
    Moribund Sacrifice                                21           12            5            8                                     
    Natural Death                                      8           11            4           10                                     
    Accidently Killed                                                            1                                                  
  Survivors                                                                                                                         
    Terminal Sacrifice                                17           23           36           28                                     
  Animals Examined Microscopically                    56           56           56           56                                     
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ALIMENTARY SYSTEM                                                                                                                  
                                                                                                                                    
   Esophagus                                          (55)         (56)         (56)         (56)                                   
      Ectasia                                                       1 (2%)                                                          
   Intestine Large, Colon                             (55)         (55)         (56)         (55)                                   
      Infiltration Cellular, Lipocyte                                                         1 (2%)                                
   Intestine Large, Rectum                            (54)         (54)         (55)         (55)                                   
      Inflammation                                                                            1 (2%)                                
   Intestine Large, Cecum                             (54)         (51)         (54)         (53)                                   
      Inflammation                                                                            1 (2%)                                
   Intestine Small, Duodenum                          (54)         (54)         (56)         (55)                                   
      Ectopic Tissue                                                                          1 (2%)                                
      Hyperplasia                                                                             1 (2%)                                
      Inflammation                                                                            1 (2%)                                
   Intestine Small, Ileum                             (53)         (46)         (53)         (52)                                   
      Hemorrhage                                       1 (2%)                                                                       
      Hyperplasia, Lymphoid                                                      1 (2%)                                             
   Liver                                              (55)         (56)         (56)         (56)                                   
      Basophilic Focus                                 9 (16%)     11 (20%)      6 (11%)      7 (13%)                               
      Basophilic Focus, Multiple                       6 (11%)     11 (20%)     26 (46%)     22 (39%)                               
      Clear Cell Focus                                 3 (5%)       1 (2%)       8 (14%)      2 (4%)                                
      Clear Cell Focus, Multiple                       2 (4%)       9 (16%)      8 (14%)      3 (5%)                                
      Congestion                                       3 (5%)       2 (4%)                    7 (13%)                               
      Cytoplasmic Alteration                           1 (2%)                                                                       
      Degeneration, Cystic                             4 (7%)      12 (21%)     15 (27%)      4 (7%)                                
      Developmental Malformation                       1 (2%)                                                                       
      Eosinophilic Focus                               5 (9%)       7 (13%)      8 (14%)      2 (4%)                                
      Eosinophilic Focus, Multiple                     1 (2%)       4 (7%)      10 (18%)      4 (7%)                                
      Fatty Change                                     5 (9%)      12 (21%)      7 (13%)     14 (25%)                               
      Hemorrhage                                       2 (4%)       3 (5%)                                                          
      Hepatodiaphragmatic Nodule                       1 (2%)       2 (4%)                                                          
      Infiltration Cellular, Lymphocyte                                                       1 (2%)                                
      Inflammation                                     1 (2%)       1 (2%)       1 (2%)       1 (2%)                                
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    8                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
ALIMENTARY SYSTEM - CONT                                                                                                            
      Mixed Cell Focus                                 1 (2%)       4 (7%)       2 (4%)       4 (7%)                                
      Mixed Cell Focus, Multiple                       2 (4%)                    2 (4%)                                             
      Necrosis                                         2 (4%)       4 (7%)       2 (4%)       2 (4%)                                
      Pigmentation                                                  1 (2%)                                                          
      Bile Duct, Hyperplasia                           3 (5%)                    3 (5%)                                             
   Mesentery                                          (6)          (1)          (4)          (10)                                   
      Fat, Necrosis                                    6 (100%)     1 (100%)     4 (100%)     8 (80%)                               
   Pancreas                                           (55)         (56)         (56)         (56)                                   
      Ectopic Liver                                                              1 (2%)                                             
      Infiltration Cellular, Lymphocyte                2 (4%)                    1 (2%)                                             
      Inflammation                                                  1 (2%)                    2 (4%)                                
      Acinar Cell, Atrophy                            33 (60%)     32 (57%)     36 (64%)     32 (57%)                               
      Acinar Cell, Hyperplasia                         1 (2%)                                                                       
      Artery, Inflammation                                                       2 (4%)                                             
      Duct, Ectasia                                                 1 (2%)       1 (2%)                                             
   Pharynx                                                         (1)                                                              
      Palate, Hyperplasia, Squamous                                 1 (100%)                                                        
   Salivary Glands                                    (56)         (55)         (56)         (56)                                   
      Abscess                                                                                 1 (2%)                                
      Infiltration Cellular, Lymphocyte                                          1 (2%)                                             
   Stomach, Forestomach                               (55)         (56)         (56)         (56)                                   
      Hyperplasia                                      4 (7%)       3 (5%)       5 (9%)       3 (5%)                                
      Inflammation                                     1 (2%)       4 (7%)       3 (5%)       1 (2%)                                
      Ulcer                                            5 (9%)       3 (5%)       2 (4%)       3 (5%)                                
      Ulcer, Multiple                                               2 (4%)       2 (4%)                                             
   Stomach, Glandular                                 (55)         (56)         (56)         (55)                                   
      Hyperplasia                                                   1 (2%)                                                          
      Inflammation                                                  1 (2%)       1 (2%)       2 (4%)                                
      Necrosis                                         3 (5%)       3 (5%)                                                          
      Ulcer                                            1 (2%)                                 3 (5%)                                
      Ulcer, Multiple                                  2 (4%)       1 (2%)       1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 CARDIOVASCULAR SYSTEM                                                                                                              
                                                                                                                                    
   Heart                                              (56)         (56)         (56)         (56)                                   
      Cardiomyopathy                                  42 (75%)     53 (95%)     55 (98%)     51 (91%)                               
      Inflammation                                                  2 (4%)                                                          
      Atrium, Dilatation                               1 (2%)                                 1 (2%)                                
      Atrium, Thrombosis                               2 (4%)       1 (2%)       2 (4%)       2 (4%)                                
      Valve, Inflammation                                           1 (2%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page    9                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 ENDOCRINE SYSTEM                                                                                                                   
                                                                                                                                    
   Adrenal Cortex                                     (55)         (56)         (56)         (56)                                   
      Angiectasis                                                                1 (2%)                                             
      Congestion                                       1 (2%)                                 1 (2%)                                
      Cytoplasmic Alteration                           1 (2%)                                 1 (2%)                                
      Degeneration                                     3 (5%)       1 (2%)       1 (2%)       2 (4%)                                
      Hyperplasia                                      7 (13%)      4 (7%)       6 (11%)      3 (5%)                                
      Hypertrophy                                      1 (2%)       3 (5%)       2 (4%)       2 (4%)                                
      Vacuolization Cytoplasmic                        7 (13%)     19 (34%)     15 (27%)     16 (29%)                               
   Adrenal Medulla                                    (54)         (55)         (56)         (56)                                   
      Angiectasis                                      1 (2%)                                                                       
      Hyperplasia                                     15 (28%)     14 (25%)     19 (34%)     12 (21%)                               
   Islets, Pancreatic                                 (8)          (9)          (5)          (5)                                    
      Hyperplasia                                      4 (50%)      3 (33%)      2 (40%)      1 (20%)                               
   Parathyroid Gland                                  (49)         (50)         (48)         (52)                                   
      Hyperplasia                                      4 (8%)       6 (12%)      3 (6%)                                             
   Pituitary Gland                                    (55)         (56)         (56)         (55)                                   
      Hemorrhage                                                    1 (2%)                                                          
      Pars Distalis, Angiectasis                       1 (2%)       7 (13%)      4 (7%)       4 (7%)                                
      Pars Distalis, Cyst                              2 (4%)       5 (9%)       4 (7%)       3 (5%)                                
      Pars Distalis, Hemorrhage                                     1 (2%)       1 (2%)                                             
      Pars Distalis, Hyperplasia                      11 (20%)     22 (39%)     25 (45%)     18 (33%)                               
      Pars Intermedia, Angiectasis                     1 (2%)                                                                       
      Pars Intermedia, Cyst                                         1 (2%)                                                          
   Thyroid Gland                                      (55)         (56)         (56)         (56)                                   
      C-Cell, Hyperplasia                              8 (15%)      5 (9%)       5 (9%)       3 (5%)                                
      Follicle, Dilatation                             4 (7%)                                                                       
      Follicular Cell, Hyperplasia                     1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENERAL BODY SYSTEM                                                                                                                
                                                                                                                                    
   None                                                                                                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 GENITAL SYSTEM                                                                                                                     
                                                                                                                                    
   Epididymis                                         (56)         (56)         (56)         (56)                                   
      Atrophy                                          1 (2%)                    1 (2%)                                             
      Granuloma Sperm                                  1 (2%)       2 (4%)       1 (2%)       1 (2%)                                
      Hypospermia                                     20 (36%)     26 (46%)     25 (45%)     29 (52%)                               
      Inflammation                                     2 (4%)                    2 (4%)                                             
      Inflammation, Chronic                            1 (2%)                                                                       
      Spermatocele                                     2 (4%)                                                                       
   Preputial Gland                                    (54)         (56)         (56)         (56)                                   
      Abscess                                          1 (2%)                                 1 (2%)                                
      Degeneration                                                               1 (2%)                                             
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   10                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
GENITAL SYSTEM - CONT                                                                                                               
      Ectasia                                         43 (80%)     49 (88%)     49 (88%)     41 (73%)                               
      Hyperplasia                                                   1 (2%)       3 (5%)       1 (2%)                                
      Inflammation                                    11 (20%)      9 (16%)     12 (21%)     16 (29%)                               
   Prostate                                           (56)         (56)         (56)         (56)                                   
      Abscess                                          1 (2%)                                                                       
      Atrophy                                          1 (2%)                                                                       
      Concretion                                       6 (11%)      7 (13%)      7 (13%)     10 (18%)                               
      Congestion                                                                 1 (2%)                                             
      Hyperplasia                                      5 (9%)       4 (7%)       6 (11%)      4 (7%)                                
      Inflammation                                    32 (57%)     24 (43%)     23 (41%)     25 (45%)                               
      Vacuolization Cytoplasmic                                                               1 (2%)                                
      Epithelium, Cytoplasmic Alteration               1 (2%)       2 (4%)                                                          
   Seminal Vesicle                                    (55)         (56)         (56)         (56)                                   
      Depletion Cellular                              22 (40%)     23 (41%)     23 (41%)     31 (55%)                               
      Ectasia                                                       1 (2%)                    1 (2%)                                
      Inflammation                                     1 (2%)                                 2 (4%)                                
   Testes                                             (56)         (56)         (56)         (56)                                   
      Atrophy                                          8 (14%)      6 (11%)      6 (11%)      8 (14%)                               
      Degeneration                                                  1 (2%)                                                          
      Hypospermia                                                   1 (2%)                    1 (2%)                                
      Arteriole, Inflammation                          1 (2%)       6 (11%)     10 (18%)      5 (9%)                                
      Bilateral, Atrophy                              10 (18%)      2 (4%)       4 (7%)       7 (13%)                               
      Bilateral, Degeneration                                       1 (2%)                                                          
      Interstitial Cell, Hyperplasia                  16 (29%)     12 (21%)     12 (21%)     14 (25%)                               
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 HEMATOPOIETIC SYSTEM                                                                                                               
                                                                                                                                    
   Bone Marrow                                        (55)         (55)         (56)         (56)                                   
      Congestion                                                                              1 (2%)                                
      Hemorrhage                                                                 1 (2%)                                             
      Hyperplasia                                     16 (29%)     15 (27%)      8 (14%)     15 (27%)                               
      Pigmentation                                                                            1 (2%)                                
   Lymph Node                                         (5)                                    (1)                                    
      Deep Cervical, Inflammation                                                             1 (100%)                              
      Lumbar, Hyperplasia, Plasma Cell                 1 (20%)                                                                      
      Renal, Hemorrhage                                                                       1 (100%)                              
   Lymph Node, Bronchial                              (47)         (43)         (40)         (39)                                   
      Hemorrhage                                      10 (21%)     18 (42%)     18 (45%)     18 (46%)                               
      Hyperplasia, Plasma Cell                         1 (2%)                                                                       
      Infiltration Cellular, Histiocyte                                                       1 (3%)                                
      Inflammation                                                  1 (2%)                                                          
      Pigmentation                                     1 (2%)       3 (7%)       2 (5%)       3 (8%)                                
   Lymph Node, Mandibular                             (55)         (55)         (56)         (56)                                   
      Cyst                                                          1 (2%)       2 (4%)                                             
      Hemorrhage                                       6 (11%)      4 (7%)       7 (13%)      3 (5%)                                
      Hyperplasia, Lymphoid                                         1 (2%)                    1 (2%)                                
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   11                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
HEMATOPOIETIC SYSTEM - CONT                                                                                                         
      Hyperplasia, Plasma Cell                         3 (5%)       7 (13%)      6 (11%)      4 (7%)                                
      Infiltration Cellular, Histiocyte                                          1 (2%)                                             
      Pigmentation                                                  1 (2%)                    1 (2%)                                
   Lymph Node, Mesenteric                             (55)         (56)         (56)         (54)                                   
      Hemorrhage                                       4 (7%)      12 (21%)      5 (9%)       7 (13%)                               
   Lymph Node, Mediastinal                            (55)         (52)         (52)         (55)                                   
      Depletion Lymphoid                                                                      1 (2%)                                
      Hemorrhage                                      22 (40%)     36 (69%)     33 (63%)     36 (65%)                               
      Hyperplasia, Lymphoid                                                      1 (2%)                                             
      Hyperplasia, Plasma Cell                         3 (5%)       2 (4%)                    2 (4%)                                
      Infiltration Cellular, Histiocyte                                          1 (2%)       1 (2%)                                
      Pigmentation                                     5 (9%)      14 (27%)     13 (25%)     12 (22%)                               
   Spleen                                             (56)         (55)         (56)         (55)                                   
      Congestion                                       1 (2%)       2 (4%)                    1 (2%)                                
      Degeneration, Cystic                                                       2 (4%)       5 (9%)                                
      Developmental Malformation                                                              1 (2%)                                
      Fibrosis                                                      1 (2%)       2 (4%)                                             
      Hematopoietic Cell Proliferation                 4 (7%)       6 (11%)      5 (9%)      13 (24%)                               
      Hemorrhage                                                                 1 (2%)                                             
      Inflammation                                                                            1 (2%)                                
      Necrosis                                                                                1 (2%)                                
      Capsule, Fibrosis                                             1 (2%)                                                          
   Thymus                                             (51)         (56)         (55)         (54)                                   
      Atrophy                                         35 (69%)     43 (77%)     42 (76%)     41 (76%)                               
      Congestion                                                                              2 (4%)                                
      Cyst                                                                                    1 (2%)                                
      Hemorrhage                                       3 (6%)       8 (14%)      2 (4%)       3 (6%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 INTEGUMENTARY SYSTEM                                                                                                               
                                                                                                                                    
   Mammary Gland                                      (52)         (53)         (56)         (53)                                   
      Galactocele                                      1 (2%)       2 (4%)                    4 (8%)                                
      Hyperplasia                                      1 (2%)                                 1 (2%)                                
      Inflammation                                     1 (2%)                                 1 (2%)                                
      Lactation                                       13 (25%)     18 (34%)     10 (18%)     16 (30%)                               
      Pigmentation                                     2 (4%)       1 (2%)                                                          
   Skin                                               (56)         (56)         (56)         (56)                                   
      Inflammation                                     1 (2%)                                                                       
      Pinna, Parakeratosis                                          1 (2%)                                                          
      Subcutaneous Tissue, Abscess                                  1 (2%)                    1 (2%)                                
      Tail, Hyperkeratosis                                                                    1 (2%)                                
____________________________________________________________________________________________________________________________________
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   12                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 MUSCULOSKELETAL SYSTEM                                                                                                             
                                                                                                                                    
   Bone                                               (56)         (56)         (56)         (56)                                   
      Calvarium, Hemorrhage                                         1 (2%)                                                          
      Coccygeal, Fracture                                           1 (2%)                                                          
      Cranium, Hemorrhage                              1 (2%)                                                                       
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 NERVOUS SYSTEM                                                                                                                     
                                                                                                                                    
   Brain                                              (56)         (56)         (56)         (56)                                   
      Compression                                      9 (16%)     17 (30%)      6 (11%)     22 (39%)                               
      Hemorrhage                                       2 (4%)       2 (4%)       1 (2%)       1 (2%)                                
      Hydrocephalus                                    4 (7%)       3 (5%)       1 (2%)       2 (4%)                                
      Infiltration Cellular, Lymphocyte                             1 (2%)                                                          
      Necrosis                                                                   1 (2%)                                             
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 RESPIRATORY SYSTEM                                                                                                                 
                                                                                                                                    
   Larynx                                             (56)         (56)         (56)         (56)                                   
      Foreign Body                                     1 (2%)                                 1 (2%)                                
      Infiltration Cellular, Lymphocyte                3 (5%)                    1 (2%)       2 (4%)                                
      Inflammation                                     3 (5%)       2 (4%)       4 (7%)       4 (7%)                                
      Epithelium, Hyperplasia                          1 (2%)       1 (2%)       1 (2%)       1 (2%)                                
   Lung                                               (56)         (56)         (56)         (56)                                   
      Congestion                                       4 (7%)       5 (9%)       3 (5%)       3 (5%)                                
      Hemorrhage                                       9 (16%)     15 (27%)      4 (7%)       3 (5%)                                
      Infiltration Cellular, Histiocyte                             1 (2%)                    1 (2%)                                
      Inflammation                                     3 (5%)       8 (14%)      3 (5%)       6 (11%)                               
      Leukocytosis                                     1 (2%)       1 (2%)                                                          
      Necrosis                                                      1 (2%)                                                          
      Alveolar Epithelium, Hyperplasia                 5 (9%)      11 (20%)     28 (50%)     38 (68%)                               
      Arteriole, Inflammation                                                    1 (2%)                                             
      Artery, Inflammation                                                       1 (2%)                                             
      Artery, Thrombosis                                            1 (2%)       1 (2%)                                             
      Bronchus, Hyperplasia                            1 (2%)                                                                       
      Goblet Cell, Hyperplasia                                      1 (2%)                                                          
   Nose                                               (55)         (55)         (56)         (56)                                   
      Angiectasis                                      7 (13%)      4 (7%)       1 (2%)       2 (4%)                                
      Foreign Body                                     6 (11%)      3 (5%)       3 (5%)       2 (4%)                                
      Hemorrhage                                       5 (9%)                    2 (4%)       1 (2%)                                
      Infiltration Cellular, Lymphocyte                                                       2 (4%)                                
      Inflammation                                     9 (16%)     10 (18%)      7 (13%)     11 (20%)                               
      Polyp Inflammatory                               1 (2%)                                                                       
      Goblet Cell, Hyperplasia                                      3 (5%)       3 (5%)       1 (2%)                                
      Nasolacrimal Duct, Inflammation                               3 (5%)                    2 (4%)                                
      Olfactory Epithelium, Cytoplasmic Alteration                  3 (5%)       2 (4%)       5 (9%)                                
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   13                                                              
NTP Experiment-Test: 05185-03         INCIDENCE RATES OF NONNEOPLASTIC LESIONS BY ANATOMIC SITE (a)               Report: PEIRPT03
Study Type: CHRONIC                                       ISOBUTYL NITRITE (IBN)                                  Date: 05/20/95  
Route: RESPIRATORY EXPOSURE WHOLE BODY                                                                            Time: 10:47:26  
____________________________________________________________________________________________________________________________________
         FISCHER 344 RATS MALE                     CONTROL      37.5 PPM     75 PPM       150 PPM                                   
                                                                                                                                    
____________________________________________________________________________________________________________________________________
                                                                                                                                    
RESPIRATORY SYSTEM - CONT                                                                                                           
      Respiratory Epithelium, Hyperplasia              2 (4%)       3 (5%)       4 (7%)       4 (7%)                                
      Respiratory Epithelium, Metaplasia, Squamous                  2 (4%)                                                          
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 SPECIAL SENSES SYSTEM                                                                                                              
                                                                                                                                    
   Eye                                                (1)                       (1)                                                 
      Hemorrhage                                                                 1 (100%)                                           
      Inflammation                                                               1 (100%)                                           
____________________________________________________________________________________________________________________________________
                                                                                                                                    
 URINARY SYSTEM                                                                                                                     
                                                                                                                                    
   Kidney                                             (55)         (55)         (56)         (56)                                   
      Congestion                                       1 (2%)                                 1 (2%)                                
      Cyst                                             1 (2%)       1 (2%)                    3 (5%)                                
      Hydronephrosis                                   1 (2%)                                                                       
      Inflammation                                                  1 (2%)                                                          
      Nephropathy, Chronic                            49 (89%)     52 (95%)     55 (98%)     55 (98%)                               
      Pigmentation                                     3 (5%)       2 (4%)                    5 (9%)                                
      Pelvis, Hyperplasia                              1 (2%)                                                                       
      Renal Tubule, Cytoplasmic Alteration             1 (2%)                                                                       
   Urinary Bladder                                    (56)         (55)         (56)         (55)                                   
      Calculus Micro Observation Only                  1 (2%)                                                                       
      Dilatation                                       4 (7%)       1 (2%)                    1 (2%)                                
      Infiltration Cellular, Lymphocyte                                                       1 (2%)                                
      Inflammation                                     1 (2%)       1 (2%)                                                          
      Transitional Epithelium, Hyperplasia             1 (2%)                                                                       
                                                                                                                                    
a  Number of animals examined microscopically at site and number of animals with lesion                                             
                                                             Page   14                                                              
                             ------------------------------------------------------------                                           
                             ----------              END OF REPORT             ----------                                           
                             ------------------------------------------------------------