Sustained azoospermia in squirrel monkey, Saimiri sciureus, resulting from a single intratesticular glycerol injection.

Previous studies in rats had shown that a single intratesticular injection of glycerol resulted in long-term suppression of spermatogenesis without marked alterations in hormone levels. Studies were undertaken to determine the effect of similar treatment in squirrel monkeys (Saimiri sciureus). Ten monkeys received an intratesticular injection of saline (controls) and ten of glycerol solution (treated). Semen and blood samples were obtained on a weekly or bi-weekly basis one month prior to, during the 8 months following and at 22 months after the injection. Sperm numbers in the semen samples of controls remained at 160-435 x 10(6) per ml throughout the experiment. Sperm numbers in treated animals declined to near zero within two months and remained at zero. Serum testosterone and progesterone levels were not significantly different between control and treated animals. Serum LH and FSH levels were not significantly different between control and treated animals except during months 6-8 after the injection, when levels in the treated were higher. At termination (22 months), the weights and sperm contents of epididymides of the glycerol-treated animals were highly significantly reduced. Steroidogenesis (based on amounts and kinds of steroids formed from 14C-progesterone) by testicular tissue was not altered by the glycerol treatment when measured on a per testis basis. This is the first evidence that a single intratesticular injection of glycerol results in long-term suppression of spermatogenesis in primates, without altering testicular steroidogenesis and serum hormone levels.