Studies on the Inhibition of Fetal Androgen Formation. Inhibition of Testosterone Synthesis in Rat and Rabbit Fetal Testes with Observations on Reproductive Tract Development

Groups of pregnant rats were injected with 2α-cyano-4,4,17α-trimethyl-17p-hydroxyandrost- 5-en-3-one (WIN) at varying dosage and frequency. Injections of 120-240 mg/kg body wt resulted in male fetuses with markedly reduced anogenital distances and hypospadias, but with unaffected differentiation of the reproductive ducts and of the urogenital sinus. Fetuses of rats injected with WIN or corn oil (control) at 14.5 to 16.5 days post coitum were examined on day 20.5 for testicular in vitro metabolism of 4-14C-pregnenolone and of 4-14C-dehydroepiandrosterone. Control testes converted each substrate primarily to 14C-testosterone and 14C-androstenedione. WIN-exposed testes synthesized markedly diminished amounts of 14C-testosterone and 11Candrostenedione, but accumulated Δ5-3β-hydroxysteroids: 14C-17α-hydroxypregnenolone,14Cdehydroepiandrosterone, plus residual substrate from 4-14C-pregnenolone, and 14C-androstenediol and residual substrate from 4-14C-dehydroepiandrosterone. Fetal testes of both the control and WIN groups converted 7-3H-testosterone to 3Handrostenedione in comparable amounts and as the only metabolite. Injection of WIN into rat fetuses at 15.5 days of gestation led to a high rate of resorption, diminished testicular conversion of 4-14C-pregnenolone to 14C-testosterone, reduced anogenital distances, and, in 2 fetuses, lack of prostatic and seminal vesicle bud development. The data, in substantial agreement with and an extension of Goldman's findings (Proc Soc Exp Biol Med121: 757, 1966), demonstrate inhibition of testicular Δ5-3β-hydroxysteroid dehydrogenase activity and of the development of the external genitalia following WIN injections, but unimpaired 17β-hydroxysteroid dehydrogenase activity and genital duct development. It is suggested that factors other than testicular testosterone (e.g., testicular dehydroepiandrosterone, androstenediol) participate in wolffian duct stabilization in the genetic male. WIN, administered to rats 10.5 and 13.5 days pregnant, reduced 14C-progesterone formation from 4-14Cpregnenolone by 11.5-day-old rat embryos or 14.5-day-old rat testes. Thus, rat embryos prior to gonadal or adrenal organization exhibit Δ5-3β- hydroxysteroid dehydrogenase activity. Treatment of pregnant rabbits with WIN equivocally influenced 4-14C-pregnenolone metabolism in testes of 26-day-old fetuses, but SU-8000 [3-(6-chloro-3-methyl-2-indenyl) pyridine] administration depressed the formation of 14C-testosterone, 14C-androstenedione, 14C-androstenediol and 14C-17α,20α-dihydroxy-4-pregnen-3-one. 14C-progesterone and 14C-pregnenolone accumulated in larger amounts; reproductive tract development was not affected. Our results combined with those of others suggest that SU-8000 inhibits several enzymes active in steroid synthesis. (Endocrinology89: 16, 1971)