title: Effects of oestradiol-17 beta and ethinyl oestradiol on human testicular steroidogenesis in vitro.
abstract: The inhibition of human testicular testosterone production in vitro by oestrogen was studied by measuring effects of oestradiol-17 beta and ethinyl oestradiol on the 3 beta-hydroxysteroid dehydrogenase/isomerase and the delta 4-pathway of testosterone synthesis. Progesterone, 17 alpha-hydroxyprogesterone, androstenedione and testosterone concentrations of incubation media were all depressed after oestrogen addition. To minimize differences in substrate amounts between incubations, 3H-labelled pregnenolone, progesterone, 17 alpha-hydroxyprogesterone or androstenedione was added to the incubation media. The conversion of pregnenolone, progesterone and 17 alpha-hydroxyprogesterone was inhibited by oestrogen. It is concluded that oestrogen inhibits 3 beta-hydroxysteroid dehydrogenase/isomerase, 17 alpha-hydroxylase and C17-20-lyase enzyme activities of human testicular tissue in vitro while 17 beta-ketosteroid reductase activity is unaffected.
mesh_terms: D019326:17-alpha-Hydroxyprogesterone; D000368:Aged; D000369:Aged, 80 and over; D000735:Androstenedione / Q000096:biosynthesis; D004958:Estradiol / Q000494:pharmacology*; D004997:Ethinyl Estradiol / Q000494:pharmacology*; D006801:Humans; D006908:Hydroxyprogesterones / Q000096:biosynthesis; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009919:Orchiectomy; D011374:Progesterone / Q000096:biosynthesis; D011471:Prostatic Neoplasms / Q000601:surgery; D011863:Radioimmunoassay; D013737:Testis / Q000187:drug effects / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis
chemical_list: D006908:Hydroxyprogesterones; D013739:Testosterone; D000735:Androstenedione; D004997:Ethinyl Estradiol; D011374:Progesterone; D004958:Estradiol; D019326:17-alpha-Hydroxyprogesterone