In vitro steroidogenesis in feline testes.

Abstract Testosterone was produced in vitro from pregnenolone, progesterone, 17αhydroxyprogesterone, dehydroepiandrosterone and androstenedione by supernatant fluid at 10000 × g of feline testicular homogenates. In the presence of NADPH alone, lya-hydroxylation of pregnenolone by the microsomal fraction (10000–105000 × g precipitate) was markedly enhanced, whereas in the presence of NAD alone, conversion of pregnenolone to progesterone was selectively activated, suggesting that the biosynthetic pathways of testosterone from pregnenolone were dependent upon cofactor predominantly present in the medium. According to the time course of pregnenolone metabolism in the presence of both NADPH and NAD, dehydroepiandrosterone was produced as the major end-product by the microsomal fraction through 17α-hydroxypregnenolone as the intermediate. When dehydroepiandrosterone was incubated as substrate under the same condition as above, testosterone was produced through androstenedione and 5-androstenediol. As a sharp peak in production of androstenedione was observed for the first 30 min of incubation, testosterone was produced predominantly through androstenedione for this period, and thereafter through both androstenedione and 5-androstenediol. From the results obtained, it was concluded that testosterone biosynthesis from pregnenolone in the feline testes in vitro occurred mainly along the · 5'-pathway or via 17α-hydroxypregnenolone, dehydroepiandrosterone and 5-androstenediol.