Production and effects of 7 alpha-hydroxytestosterone on testosterone and dihydrotestosterone metabolism in rat testis.
1. Testicular 7 alpha-hydroxylation of testerone was assayed in cell extracts of rats between 12 and 79 days of age. Maximal 7 alpha-hydroxylase activity was observed about 60 days, while insignificant activity was obtained prior to 42 days of age. 2. 7 alpha-Hydroxytestosterone, a major metabolite of testosterone in mature rat testis, inhibited 5 alpha-reduction of testosterone in cell extracts of mature but not of immature rat testis. 3. Maximal testicular activity of 3 beta-hydroxysteroid dehydrogenase using dihydrotestosterone as substrate was obtained in the presence of NAD, while maximal 3 alpha-hydroxysteroid dehydrogenase activity was observed with NADP. Both enzyme activites were reversible. 4. Sensitivity toward testosterone inhibition of 3-hydroxysteroid dehydrogenase varied greatly with stage of testis development being highest at 25-27 days of age. In contrast to testosterone, 7 alpha-hydroxytestosterone was an inhibitor of 3 alpha-hydroxysteroid dehydrogenase only. In the mature rat testis 7 alpha-hydroxytestosterone may be a naturally occurring inhibitor of dihydrotestosterone and 5 alpha-androstane-3 alpha, 17 beta-diol formation.
D000375:Aging; D000818:Animals; D013196:Dihydrotestosterone / Q000378:metabolism*; D006913:Hydroxysteroid Dehydrogenases / Q000378:metabolism; D006915:Hydroxytestosterones / Q000378:metabolism* / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D051381:Rats; D013250:Steroid Hydroxylases / Q000378:metabolism; D013737:Testis / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D013739:Testosterone / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology
D006915:Hydroxytestosterones; D013196:Dihydrotestosterone; D013739:Testosterone; D006913:Hydroxysteroid Dehydrogenases; D013250:Steroid Hydroxylases