Steroid metabolism in pregnant hamster. II. The metabolism of androgens by the hamster placenta.

The biotransformation of [4-14C] labelled dehydroepiandrosterone, testosterone and androstenedione by quartered placentae of 12 and 15 day pregnant hamsters was investigated in vitro. The above androgens were extensively metabolized by placental preparations and resulting products were identified by chromatographic and isotope dilution methods. The formation of 7 alpha-hydroxy-androstenedione, testosterone, 3 alpha-hydroxy-5 beta-androstan-17-one, 3 beta-hydroxy-5 alpha-androstan-17-one, androstenedione, 5alpha-androstanedione and 5 beta-androstanedione was demonstrated from androstenedione and testosterone. In addition to the above steroids 7 alpha-hydroxy-dehydroepiandrosterone was also formed in the incubations with dehydroepiandrosterone. Androstenedione was the main metabolite formed from each precursor at day 12 of gestation, while only trace amount of testosterone was detected. The most active enzymes in androgens metabolism in the hamster placenta at the second stage of gestation were 17 beta-hydroxysteroid dehydrogenase and delta 5-3 beta-hydroxysteroid dehydrogenase with delta 5 leads to 4 isomerase. Other enzymes present in the hamster placenta were 3 alpha and 3 beta-hydroxysteroid dehydrogenase and delta 4-5 alpha- and delta 4-5 beta-reductase. 7 alpha-hydroxylase was demonstrated for the first time in the animal placenta. The activity of 7 alpha-hydroxylase increased at the end of gestation while that of delta-5-3 beta-hydroxysteroid dehydrogenase decreased markedly. Aromatase activity was absent in the hamster placenta.