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Abstract
The in vitro conversion of pregnenolone was studied in testicular tissue specimens from 6 fetuses, 3 prepubertal boys with indescended testes, 5 normal adult men, and 12 elderly males with prostatic carcinoma. Adult testicular tissue converted pregnenolone to testosterone mainly along the δ5 metabolic pathway. Steroid intermediates that were converted from pregnenolone to δ4 metabolites prior to the rate limiting C17-20 lyase step were “trapped” as 17α-hydroxyprogesterone. The conversion patterns in testicular tissue from fetuses were similar to those in testicular tissue from adults and elderly men. In prepubertal testicular tissue, however, a significantly lower conversion was observed, mediated by the enzymes 3β-hydroxysteroid dehydrogenase/isomerase and 17α-hydroxylase. The conversion mediated by 17α-hydroxylase was significantly lower in testicular tissue from the elderly males than from younger adults, suggesting a relative steroidogenic insufficiency in the elderly males. Testicular tissue from an anencephalic fetus produced testosterone and steroid intermediates in vitro, although to a lesser extent than in testicular tissue from other fetuses. The enzymes 3β-hydroxysteroid dehydrogenase/isomerase and 17α-hydroxylase appeared to be under gonadotropic control.