Fertilizing ability of spermatozoa of rats treated with STS 557

Treatment with 1.0 mg of STS 557 (17 alpha-cyanomethyl-17 beta-hydroxy-estra-4.9 (10)-diene-3-one) daily for 3 weeks had no effect on the weight of the accessory genital organs of male rats. Acid phosphatase activity in ventral prostate was reduced. The fertilizing ability and motility of spermatozoa were reduced. Twenty-eight percent of the seminiferous tubules in testis were partly or completely devoid of germinal cells. Treatment with 0.5 mg of STS 557 had no significant effect.