In in vitro studies it was found that, in the presence of added NADPH, the human placenta metabolizes progesterone to 20α-hydroxy-4-pregnen-3-one at increasing rates as pregnancy advances. A fivefold increase in 20α-hydroxysteroid oxidoreductase activity is observed in term placentas compared with the enzymic activity of placentas of 12 to 20 wk gestation (368 ± 53 pmoles/mg protein/hr vs 71 ± 8pmoles/mg protein/hr). The 5α-reductase and 3β-hydroxysteroid oxidoreductase activities were similar in placentas obtained from early and late human pregnancies.
ASJC Scopus subject areas
- Obstetrics and Gynecology