Production of Hypospadias in the Rat by Selective Inhibition of Fetal Testicular 17α-Hydroxylase and C17-20-lyase

Although congenital adrenal hyperplasia due to a deficiency of 17a-hydroxylation has been described only in genetic women, one would expect genetic males with this defect to fail to masculinize in utero due to inadequate fetal testosteronogenesis. To test this hypothesis 2 drugs, Su-10,603 [7-Cl-3,4-dihydro-2-(3-pyridyl)-l(2H)-naphthalenone] and Su-8000 [3-(6chloro-3-methyl-2-indenyl)pyridine], which inhibit 17a-hydroxylase and Cn_2o-lyase selectively in rat testes, have been administered to pregnant rats. Neither drug affects maternal adrenal or fetal adrenal weights or female fetal urethral distance, presumably because 17a-hydroxylation is not involved in corticoidogenesis in this species. At maximal sublethal doses each drug produces a significant degree of hypospadias in male fetuses. Incubates of experimental testes with appropriate cofactors have more residual labeled progesterone and 17a-hydroxyprogesterone but less androstenedione, testosterone and 5a-androstan-3a,17/3-diol than those of control testes, indicating that the experimental testes have a considerable reduction in activity of 17 ahydroxylase and Cn-oo-lyase but about the same degree of activity of NADPH-dependent 17ketosteroid reductase and testosterone-5a-reductase and 3-ketosteroid reductase compared to control testes. Although the changes in testicular enzymatic activities are apparent in incubations of 100 til total volume, they only become statistically significant when the volume is reduced to 20 /A, indicating dissociation of endogenous inhibitor from enzyme occurs at higher dilutions. The present results have shown that reduction of fetal testosteronogenesis by inhibition of 17ahydroxylation and Cn_2o side chain cleavage in addition to the previously demonstrated inhibition of 2 other testosteronogenic enzymes, A,3/3hydroxysteroid dehydrogenase and cholesterol desmolase, results in failure of masculinization of male fetuses as manifested by hypospadias. (Endocrinology 88 : 527, 1971) /CONGENITAL adrenal hyperplasia due to v_>4 a deficiency of 17-hydroxylation has been described only in genetic women (1-3). 17-Hydroxylation is essential not only to the biosynthesis of cortisol but also to the formation of androgens and estrogens (4). Patients with this disease have excess production of 17-desoxycorticoids, namely, corticosterone and desoxycorticosterone, and the excess levels of the latter steroid may give rise to the hypertension of these patients. Their lack of post-pubertal sex hormone production leads to amenorrhea and failure of post-pubertal sexual development. The genitalia of these women are normal at birth, presumably because sexual differentiation of the mammalian female fetus is not dependent upon hormonal influence (5). Our work with experimental models of conReceived June 5, 1970. Supported by research grants from the National Foundation, "March of Dimes," and AM-10, 521, HD 4863 from the USPHS. 1 Recipient of Career Development Award HD13,628 from the USPHS. genital adrenal hyperplasia has indicated that testosterone may be the organizer of androgendependent male sexual differentiation, since selective inhibition of 2 other enzymes involved in fetal testicular production of testosterone results in hypospadias (4,6-8). Thus, males with a defect in 17a-hydroxylase may be expected to have this genital malformation. Su-10,603 [7-Cl-3,4-dihydro-2 (3-pyridyl)-l (2H)-naphthalenone] and Su-8000 [3-(6-chloro3-methyl-2-indenyl) pyridine] inhibit selectively 17a-hydroxylation in the adrenal of the dog in vivo and of the guinea pig and cow in vitro (9). These agents also inhibit rabbit, rat and sheep testicular 17a-hydroxylation specifically in vitro, but in the dog and rat it is possible that they also may inhibit Ci7~2o-lyase (10-13). Administration of Su-10,603 to control and adrenalectomized immature rats inhibits growth of seminal vesicles, ventral prostrates, levatores ani and uteri, without other obvious effects (13). This agent also interferes with the response of immature males (but not females) to chorionic gonadotrophin as judged by sex accessory organ weights (14). It does not affect