CATECHOLESTROGEN MODULATION OF STEROID-PRODUCTION BY RAT LUTEAL CELLS- MECHANISM OF ACTION

This study investigated the mechanisms underlying 2-hydroxyestradiol ( 2-OHE(2)) effect on luteal steroidogenesis using serum-free cultures o f mixed luteal cells from day 8 pseudopregnant rats. Initially, intera ctions between 2-OHE(2) and LH or dibutyryl (db)cAMP on progesterone p roduction were investigated. LH (2.50 ng/ml) and 2-OHE(2) (2.5 mu g/ml ) had comparable effects on progesterone accumulation, while dbcAMP (5 mM) was more stimulatory. When applied together, 2-OHE(2) did not syn ergize with LH or dbcAMP to further enhance progesterone accumulation. Furthermore, in time course experiments, the dose-dependent effect of 2-OHE(2) was to reduce and eventually abolish the time-dependent incr ease in cAMP accumulation. In contrast LH stimulated cAMP accumulation at all times. Experiments in which cells were co-treated with 2-OHE(2 ), 22-OH-cholesterol and cyanoketone, or with 2-OHE(2) and 22-OH-chole sterol or pregnenolone indicated that 2-OHE(2) not only had a stimulat ory effect on the cholesterol side-chain cleavage and 3 beta-hydroxyst eroid dehydrogenase enzymes, but it also appeared to inhibit the 20 al pha-hydroxysteroid dehydrogenase leading to a relative increase in pro gesterone accumulation. Experiments with hormone antagonists suggested that the actions of 2-OHE(2) were not mediated by the estrogen, alpha - or beta-adrenergic receptors. The results of this study support the concept of a physiological role for catecholestrogens in rat luteal st eroidogenesis.