In vitro conversion of 3H-pregnenolone by human testicular tissue from fetal age to senescence.
The in vitro conversion of pregnenolone was studied in testicular tissue specimens from 6 fetuses, 3 prepubertal boys with undescended testes, 5 normal adult men, and 12 elderly males with prostatic carcinoma. Adult testicular tissue converted pregnenolone to testosterone mainly along the delta 5 metabolic pathway. Steroid intermediates that were converted from pregnenolone to delta 4 metabolites prior to the rate limiting C17-20 lyase step were "trapped" as 17 alpha-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 3 beta-hydroxysteroid dehydrogenase/isomerase and 17 alpha-hydroxylase. The conversion mediated by 17 alpha-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 3 beta-hydroxysteroid dehydrogenase/isomerase and 17 alpha-hydroxylase appeared to be under gonadotropic control.
D015096:3-Hydroxysteroid Dehydrogenases / Q000378:metabolism; D000328:Adult; D000368:Aged; D000375:Aging; D002648:Child; D002675:Child, Preschool; D003456:Cryptorchidism / Q000378:metabolism; D005260:Female; D005333:Fetus / Q000378:metabolism*; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008875:Middle Aged; D011247:Pregnancy; D011284:Pregnenolone / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism; D011627:Puberty; D013254:Steroid 17-alpha-Hydroxylase / Q000378:metabolism; D013737:Testis / Q000196:embryology / Q000378:metabolism*; D013739:Testosterone / Q000097:blood
D013739:Testosterone; D011284:Pregnenolone; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D015096:3-Hydroxysteroid Dehydrogenases; D013254:Steroid 17-alpha-Hydroxylase