Catecholestrogen modulation of steroid production by rat luteal cells: Mechanism of action

Abstract

This study investigated the mechanisms underlying 2-hydroxyestradiol (2-OHE 2) effect on luteal steroidogenesis using serum-free cultures of mixed luteal cells from day 8 pseudopregnant rats. Initially, interactions between 2-OHE 2 and LH or dibutyryl (db)cAMP on progesterone production were investigated. LH (250 ng/ml) and 2-OHE 2 (2.5 μg/ml) had comparable effects on progesterone accumulation, while dbcAMP (5 mM) was more stimulatory. When applied together, 2-OHE 2 did not synergize 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 increase 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-cholesterol or pregnenolone indicated that 2-OHE 2 not only had a stimulatory effect on the cholesterol side-chain cleavage and 3β-hydroxysteroid dehydrogenase enzymes, but it also appeared to inhibit the 20α-hydroxysteroid dehydrogenase leading to a relative increase in progesterone accumulation. Experiments with hormone antagonists suggested that the actions of 2-OHE 2 were not mediated by the estrogen, α- or β-adrenergic receptors. The results of this study support the concept of a physiological role for catecholestrogens in rat luteal steroidogenesis.