Regulation of progesterone biosynthesis in the human placenta by estradiol 17 beta and progesterone.

Ex vivo addition of estradiol 17 beta to first trimester or term human placental minces caused a significant increase in the quantity of progesterone produced. Addition of an aromatase inhibitor, CGS 16949 A, or the estrogen receptor antagonist, ICI 182780, significantly inhibited progesterone production confirming the role of estradiol 17 beta in the regulation of progesterone synthesis in human placenta. RU 486 and ZK 98299, which are antagonists of progesterone receptor, significantly modulated progesterone synthesis in the human placenta but exhibited paradoxical effects on the first trimester and term placenta. We conclude that progesterone synthesis in the human placenta is regulated by estradiol 17 beta and progesterone. This is the first report providing evidence for autoregulation of progesterone synthesis in the human placenta.