Testicular steroidogenesis in the baboon Papio anubis.
We recently reported that the baboon testis converts pregnenolone to testosterone through the delta-4 pathway. The present studies were to determine the metabolism of intermediates of the delta-4 and delta-5 pathway by the baboon testis. Fragments (50 mg) were incubated for 3 hr with 10 muCi of the following tritium-labelled substrates: pregnenolone, progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone, dehydroepiandrosterone, androstenedione, or testosterone. Pregnenolone was converted to testosterone primarily through the delta-4 pathway, with accumulation of progesterone, 17-hydroxyprogesterone and 20alpha-dihydroprogesterone as predominant intermediates. Similar results were obtained in progesterone incubations. 17-hydroxyprogesterone was not efficiently metabolized by the fragments, while 17-hydroxypregnenolone and dehydroepiandrosterone were efficiently converted into testosterone and androstenedione. Androstenedione was metabolized primarily to testosterone, while testosterone was not a suitable substrate. Some 5alpha-androstanediol was identified in each incubate. These results suggest that although testosterone is formed from pregnenolone through the delta-4 pathway, the delta-5 intermediates are more suitable substrates for testosterone synthesis in the baboon testis.
D006907:17-alpha-Hydroxypregnenolone / Q000378:metabolism; D000735:Androstenedione / Q000378:metabolism; D000818:Animals; D003687:Dehydroepiandrosterone / Q000378:metabolism; D000882:Haplorhini; D006908:Hydroxyprogesterones / Q000378:metabolism; D066298:In Vitro Techniques; D008297:Male; D010215:Papio; D011284:Pregnenolone / Q000378:metabolism; D011374:Progesterone / Q000378:metabolism; D013737:Testis / Q000378:metabolism*; D013739:Testosterone / Q000096:biosynthesis* / Q000378:metabolism
D006908:Hydroxyprogesterones; D006907:17-alpha-Hydroxypregnenolone; D013739:Testosterone; D000735:Androstenedione; D003687:Dehydroepiandrosterone; D011374:Progesterone; D011284:Pregnenolone