Evaluation of STS-557 as an oral contraceptive in male rat

Development of male‐fertility‐regulating agents

“…"Pure" antiandrogens16 such as cyproterone (22) and flutamide (23) block the action of androgens, (26)], as an oral contraceptive in male rats and monkeys has been carried out. "TU It revealed that although STS-557 is a potent inhibitor of spermatogenesis, its inhibitory effect on Leydig's cell function is a contradiction for its use as a male oral contraceptive.…”

Effect of STS‐557 (17α‐cyanomethyl 17β‐hydroxy‐estra‐4, 9(10)‐dien‐3‐one) on blood hormone levels, the testis, accessory sex organs and fertility of rats

“…The reduction in plasma levels of FSH and LH after 4 weeks of treatment in spite of a very low level of testosterone indicated a direct action of STS-557 on the pituitary, affecting the normal feedback mechanisms. Srivastava et al (1987) reported a decrease in seminiferous tubule diameter and arrest of spermatogenesis beyond the primary spermatocyte stage after oral adrninistration of STS-557. Our study confirms their findings and the measurement of spermatogenesis at stage VII carried out in the present study also specifically demonstrated a drastic reduction in the number of step 7 spermatids together with a reduction in tubule diameter.…”

“…Introduction STS-557. a potent progestin but having weak antiandrogenic properties (Dorner et al, 1977;Srivastava et al, 1987), offers a new approach to fertility regulation in the male. The drug interrupts spermatogenesis, reduces the motility and fertilizing ability of sperm and causes regressive changes in the accessory sex organs of rodents (Oettel et ul., 1980(Oettel et ul., , 1983Warikoo & Das, 1983;Srivastava er al., 1987) and primates (Majumdar et al, 1988).…”