In vitro metabolism of [4-14C] androstenedione and [4-14C] testosterone by rabbit placenta

The metabolism of labelled androstenedione and testosterone in rabbit placenta on day 15 and 28 of gestation was studied in vitro. Extensive ring A reduction was observed. 5beta-Androstane-3alpha,17beta-diol,5beta-androstane-3beta,17beta-diol, 3alpha-hydroxy-5beta-androstan-17-one, 3beta-hydroxy-5beta-androstane-17-one, 17beta-hydroxy-5beta-androstan-3-one and 5beta-androstane-3, 17-dione were formed from androstenedione as proved by crystallization method. Testosterone was metabolized to 5beta-androstane-3alpha,17beta-diol, 5beta-androstane-3beta,17beta-diol and 17beta-hydroxy-5beta-androstan-3-one. The formation of estrogens was not found from any precursor. The results indicate that the rabbit placenta in the mid and late gestation shows delta4-5beta-reductase, 17beta-, 3alpha-and 3beta-hydroxysteroid dehydrogenase activities.