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Abstract for RACB94006

Reproductive Toxicity of Caffeine Administered by Gavage to Sprague-Dawley Rats

CASRN: 58-08-2
Chemical Formula: C8H10N4O2
Molecular Weight: 194.19
Report Date: June 28, 1996

Abstract

The following abstract presents results of a study conducted by a contract laboratory for the National Toxicology Program. The findings were not evaluated in accordance with the levels of evidence for reproductive or developmental criteria established by NTP in March 2009. The findings and conclusions for this study should not be construed to represent the views of NTP or the U.S. Government.

The potential reproductive toxicity of caffeine in Sprague-Dawley rats was evaluated using the Reproductive Assessment by Continuous Breeding (RACB) protocol. Based on decreased body weights and feed consumption, increased water consumption, and mortality noted during Task 1, dose levels for the continuous breeding phase for this study were set at 12.5, 25, and 50 mg/kg.

Male and female Sprague-Dawley rats were exposed to caffeine in deionized water by oral gavage at a dose volume of 5 ml/kg. Individual dose volumes were adjusted weekly. During 16 weeks of cohabitation, live pup weight adjusted for litter size was decreased by 7, 7, and 8% in the 12.5, 25, and 50 mg/kg dose groups, respectively. No differences were observed in other reproductive endpoints.

A crossover mating trial (Task 3) revealed no changes on male or female fertility or in pup weight. Reproductive parameters were comparable between dose groups when naive males were mated with control or 50 mg/kg females and when naive females were mated with control or 50 mg/kg males.

The decreased pup weight was observed concomitant with reduced dam weight gain. Throughout the study, the body weights were less than controls in the F0 12.5 (4-7%), 25 (9-15%), and 50 (9-18%) mg/kg males and 12.5 (5-18%), 25 (5-19%), and 50 (8-19%) mg/kg females. Mean feed consumption (g/animal/day) was decreased by approximately 17 and 20% in the 25 and 50 mg/kg animals of both sexes, respectively, during the first week of the study. At necropsy, no differences were noted in F0 male or female absolute organ weight data; however, many relative organ weights (mg/g body weight) were increased in all dosed groups when compared to controls. These differences were attributed to the decrease in terminal body weights. No treatment-related gross or microscopic lesions were observed in the F0 animals.

Evaluation of F0 computer-assisted sperm analysis (CASA) data revealed a treatment-related decrease (3%) in percent motile sperm in the 50 mg/kg F0 males compared to controls. The sperm velocity (mm/sec) was decreased (7-12%) in all treated males. The average radius (m) was also decreased (22-36%) in all treated males. The percent normal sperm was decreased slightly in the 50 mg/kg males when compared to controls. The remaining sperm endpoints were comparable among all groups.

In Task 4 (second generation evaluation), no treatment-related differences were observed in pup weights during lactation (PND 1-21). From the initiation of dosing (PND 22) through the maturation phase up to the termination of Task 4, mean body weights of the F1 low-to-high dose males and females were decreased by approximately 12%, 18%, and 23% when compared to controls. Mean feed consumption values (g/animal/day) were decreased (5-19%) in all treated groups during Task 4. No mortality was observed in any of the F1 animals.

Measures of reproductive performance of second generation breeding pairs revealed a decrease in the number of live F2 pups per litter (21%) and proportion of pups born alive (4%) in the 50 mg/kg dose group. No differences were observed between dose groups in other endpoints.

At necropsy, many decreases were noted in F1 absolute organ weight data and many increases in F1 relative organ weights were observed in all treated groups when compared to controls. These differences may be attributed to the decreased terminal body weights. No treatment-related gross or microscopic lesions were observed in the F1 animals.

As observed in the F0 males, a decrease in percent motile sperm (4%) and sperm velocity (9%) was observed in the 50 mg/kg F1 males compared to controls. The average radius (m) was also decreased (23-26%) in the 25 and 50 mg/kg groups. The remaining sperm parameters were unchanged.

Results of this study show that caffeine is not a selective reproductive toxicant, because the minor effects on sperm motion parameters and pup weight/viability occurred concomitant with, or at doses greater than, those doses that reduced body weight gain. It was demonstrated that exposure to caffeine reduced pup weights in the F0 females at greater than or equal to 12.5 mg/kg and litter size and viability in the F1 generation at 50 mg/kg. The delay to conception observed in humans consuming caffeine (Wilcox, 1988, Williams, 1990, Christianson, 1989) was not observed in this study. The no-observable-adverse-effect level (NOAEL) was not established in this study as the 12.5 mg/kg animals displayed reduced body weight gain.

NTIS# PB96-211743

Studies

SUMMARY OF RESULTS CAFFEINE: REPRODUCTIVE ASSESSMENT BY CONTINUOUS BREEDING WHEN ADMINISTERED TO SPRAGUE-DAWLEY RATS BY ORAL GAVAGE
  Treatment Group (mg/kg)
Parameters Control (0) Low (12.5) Mid (25) High (50)
 
General Toxicity (Tasks 2 and 3)
Terminal Body Weight - decreaseF decreaseM,F decreaseM,F
Feed Consumption (g/animal/day)
Males (Week 18) - - decreaseM decreaseM
Females (PND 4, 7, 14, and 21) - - - -
Absolute Kidneys Weight - - - -
Relative Kidneys Weight - increaseM,F increaseM,F increaseM,F
Absolute Liver Weight - - - -
Relative Liver Weight - increaseF increaseF increaseM,F
Mortality 0M,1F 0M,2F 0M,0F 0M,0F
Reproductive Parameters (Task 2)
Average Litters per Pair - - - -
Average Live Pups per Litter - - - -
Proportion of Pups Born Alive - - - -
Adjusted Live Pup Weighta - decreaseM,F decreaseM,F decreaseM,F
Cumulative Days to Litter - - - -
Progression of Toxicity (Task 2)
Mean Live Pups per Litter - - - -
Pregnancy Index - - - -
Male Crossover Mating - Naive Females x Treated Males (Task 3)
Mating Index -     -
Pregnancy Index -     -
Fertility Index -     -
Live Pups per Litter -     -
Proportion of Pups Born Alive -     -
Adjusted Live Pup Weighta -     -
Gestation Length -     -
Number of Resorptions per Litter -     -
Post-implantation Loss -     -
Female Crossover Mating - Naive Males x Treated Females (Task 3)
Mating Index -     -
Pregnancy Index -     -
Fertility Index -     -
Live Pups per Litter -     -
Proportion of Pups Born Alive -     -
Adjusted Live Pup Weighta -     -
Gestation Length -     -
Estrous Cycle Length -     -
Necropsy (Tasks 2/3)
Ovarian Weight - - - -
Right Testis Weight - - - -
Right Epididymis Weight - - - -
Right Caudal Epididymis Weight - - - -
Prostate Weight - - - -
Seminal Vesicles w/C.G. Weight - - - -
Vas Deferens Sperm Motion Parameters (CASA)
Percent Motile Sperm - - - decrease
Velocity - decrease decrease decrease
Average Radius - decrease decrease decrease
Epididymal Sperm Density - - - -
Epididymal Sperm Morphology, % Abnormal - - - increase
No. Spermatids per mg Testis - - - -
Total No. Spermatid Heads per Testis - - - -
Second Generation (Task 4)
Pup Survival - - - -
Body Weight (21 days) - decreaseF decreaseM,F -
Body Weight (81±12 days) - decreaseM,F decreaseM,F decreaseM,F
General Toxicity (Task 4)
Terminal Body Weight - decreaseM,F decreaseM,F decreaseM,F
Feed Consumption (g/animal/day)
Males and Females (Task Week 2) - decreaseM,F decreaseM,F decreaseM,F
Absolute Kidneys Weight - decreaseF decreaseM,F decreaseM,F
Relative Kidneys Weight - - increaseM,F increaseM,F
Absolute Liver Weight - decreaseM,F decreaseM,F decreaseM,F
Relative Liver Weight - - decreaseM decreaseM
Mortality 0M,0F 0M,0F 0M,0F 0M,0F
Reproductive Parameters (Task 4)
Mating Index - - - -
Pregnancy Index - - - -
Fertility Index - - - -
Live Pups per Litter - - - decrease
Proportion of Pups Born Alive - - - decrease
Adjusted Live Pup Weighta - - - -
Gestation Length - - - -
Estrous Cycle Length - - - -
Necropsy (Task 4)
Ovarian Weight - - - -
Right Testis Weight - decrease decrease decrease
Right Epididymis Weight - - decrease -
Right Caudal Epididymis Weight - - - -
Prostate Weight - - - -
Seminal Vesicles w/C.G. Weight - - - -
Vas Deferens Sperm Motion Parameters (CASA)
Percent Motile Sperm - - - decrease
Velocity - - - decrease
Average Radius - - decrease decrease
Epididymal Sperm Density - - - -
Epididymal Sperm Morphology, % Abnormal - - - -
No. Spermatids per mg Testis - - - -
Total No. Spermatid Heads per Testis - - - -

_______________________________________________
a Live pup weight adjusted for litter size

KEY: M = Male increase = Significant increase in the parameter
  F = Female decrease = Significant decrease in the parameter
    - = No effect
MTD: A maximum tolerated dose (MTD) was reached for the F0 and F1 generation animals, based on decreased body weights.


REPRODUCTIVE TOXICANT:

Male - Yes, slight. Based on decreases in computer assisted sperm motion parameters (sperm motility, velocity, and average radius) noted in both F0 and F1 males. Male fertility was not affected.

 

Female - Yes (reproductive/developmental), based on reduced pup weights in Task 2 and decreased pup number and viability in Task 4.

CLASSIFICATION:

      12.5 mg/kg 25 mg/kg 50 mg/kg
  Males Reproductive Toxicity + + +
    General Toxicity + + +
 
  Females Reproductive/Developmental Toxicity + + +
    General Toxicity + + +