Reproductive System, Male

Epididymis - Hypospermia

Narrative

Comment:

Reduced sperm content is generally caused by reduced testicular spermatogenesis but can also be due to an obstructive lesion in the efferent ducts preventing sperm from a normal-appearing testis from reaching the epididymis. Sperm normally reach the cauda in 3-5 days and remain stored there for a week or more. Some toxicants can cause a decrease in transit time, thereby reducing normal sperm content (with no effect on spermatogenesis). Reduced testosterone levels will also result in reduced survival of sperm in the epididymis. A reduction in sperm is often accompanied by an increase in sloughed testicular germ cells and cell debris, due to associated spermatogenic disturbances in the testis. A reduction in sperm content is also often associated with a reduction in the size of the ductal lumen (ductal atrophy) due to the reduced volume of sperm and fluid. There may be a reduction (oligospermia) or a total absence (aspermia) of sperm; the degree of reduction can be represented using severity grades. Peripubertal rats (8-10 weeks) and mice (5-7 weeks) may have normal-appearing testes, normal amounts of sperm in the caput and corpus, but reduced amounts of sperm in the cauda because they have not built up full sperm reserves. This should not be considered abnormal in animals of this age.

Recommendations:

Reduced sperm content should be recorded and graded and should be discussed in the pathology narrative if the incidence and/or severity appears to be related to chemical administration. Bilateral involvement should be recorded when present. It is important to compare any potential changes with age-matched controls and to correlate with any available sperm count data. Any correlation with disturbances in testicular spermatogenesis should also be noted in the pathology narrative to aid interpretation. Correlation with any spermatogenic disturbances should also be noted in the pathology narrative to aid interpretation.

References:

Creasy D, Bube A, de Rijk E, Kandori H, Kuwahara M, Masson R, Nolte T, Reams R, Regan K, Rehm S, Rogerson P, Whitney K. 2012. Proliferative and nonproliferative lesions of the rat and mouse male reproductive system. Toxicol Pathol 40:40S-121S.

Abstract: http://www.ncbi.nlm.nih.gov/pubmed/22949412

Ezer N, Robaire B. 2002. Androgenic regulation of the structure and functions of the epididymis. In: The Epididymis: From Molecules to Clinical (Robaire B, Hinton BT, eds). New York, Kluwer/Plenum, 297-316.

Abstract: http://www.springer.com/medicine/urology/book/978-0-306-46684-7

Klinefelter GR. 2002. Actions of toxicants on the structure and function of the epididymis. In: The Epididymis: From Molecules to Clinical (Robaire B, Hinton BT, eds). New York, Kluwer/Plenum, 353-370.

Abstract: http://www.springer.com/medicine/urology/book/978-0-306-46684-7

Radovsky A, Mitsumori K, Chapin RE. 1999. Male reproductive tract. In: Pathology of the Mouse: Reference and Atlas (Maronpot RR, Boorman GA, Gaul BW, eds). Cache River Press, Vienna, IL, 381-407.

Abstract: http://www.cacheriverpress.com/books/pathmouse.htm

All Images

Epididymis - Hypospermia. A reduced number of sperm in the epididymis in a male B6C3F1 mouse from a subchronic study.

Epididymis - Hypospermia. Higher magnification of Figure 1. A reduced number of sperm in the epididymis in a male B6C3F1 mouse from a subchronic study.

Epididymis - Hypospermia. A reduced number of sperm in the epididymis in a male F344/N rat from a subchronic study.

Epididymis - Hypospermia. Higher magnification of Figure 3. There is absence of sperm in this epididymal duct in a male F344/N rat from a subchronic study.

Authors and Reviewers

Authors:

Dianne M. Creasy, PhD, Dip RCPath, FRCPath
Dianne Creasy Consulting LLC
Pipersville, PA

Robert R. Maronpot, DVM, MS, MPH, DACVP, DABT, FIATP
Senior Pathologist
Experimental Pathology Laboratories, Inc.
Research Triangle Park, NC

Dipak K. Giri, DVM, PhD, DACVP
Toxicologic Pathologist
Integrated Laboratory Systems, Inc.
Research Triangle Park, NC

Reviewers:

Mark F. Cesta, DVM, PhD, DACVP
Staff Scientist, NTP Pathologist
Cellular and Molecular Pathology Branch
Division of the National Toxicology Program
National Institute of Environmental Health Sciences
Research Triangle Park, NC

David E. Malarkey DVM, PhD, DACVP, FIATP
Head, National Toxicology Program Pathology Group
Cellular and Molecular Pathology Branch
Division of the National Toxicology Program
National Institute of Environmental Health Sciences
Research Triangle Park, NC