Suppression of spermatogenesis by testosterone in adult male rats: effect on fertility, pregnancy outcome and progeny.

The relationship between decreasing spermatogenic activity and fertility, pregnancy outcome and the progeny is poorly understood. To study this relationship a model where testosterone is given by a sustained release device is used. Adult male Sprague-Dawley rats received empty or testosterone-filled implants measuring 0.5, 1.0, 2.0, 3.0, 4.0 and 8.0 cm. On Day 90 and again on Day 104 each male was exposed to two females in proestrus. Twenty days later the females were killed. Corpora lutea, implantation sites, resorptions and live normal and abnormal fetuses were counted. Sperm counts in the caput-corpus region of the epididymis in the 3.0-, 4.0- and 8.0-cm testosterone treatment groups were 12.6%, 3.0% and 29.9% of control, while those in the caudal region were 19.8%, 4.0% and 50.8% of control, respectively. The number of females with spermatozoa in the vagina after breeding was significantly diminished only in animals treated with the 4.0-cm testosterone implants (control, 95.8%; 4.0-cm, 50%) while the number of pregnant females per sperm-positive females was markedly reduced in the females mated with both the 3.0-cm and 4.0-cm testosterone implants (control, 82.6%; 3.0-cm, 10.0%; 4.0-cm, 7.7%). There was no effect on the numbers of corpora lutea, on the incidence of pre- or post-implantation loss, malformations, or on the numbers of pups/litter. Individual animals with a decrease in caudal epididymal spermatozoal reserves to less than 5 million, however, are infertile. A decrease in epididymal spermatozoal reserves mediated by testosterone does not cause an increase in teratogenicity in the resultant progeny.