Veldhuis J D
J Steroid Biochem. 1986 May;24(5):977-82. doi: 10.1016/0022-4731(86)90349-3.
Estrogen exerts biphasic effects on progesterone biosynthesis by swine granulosa cells, such that initial transient inhibition is followed by delayed but sustained stimulation. We have tested the functional role of the estradiol receptor in these biphasic responses by utilizing the highly selective estrogen-receptor antagonist, LY156758, and the synthetic estrogen agonist, moxestrol. The acute inhibitory action of estradiol was mimicked in a dose-dependent action by moxestrol (half-maximally inhibitory dose: 54.3 +/- 25 ng/ml), but was not antagonized by LY156758. Rather, the antiestrogen alone significantly suppressed basal progesterone synthesis, and accentuated the suppressive effect of submaximally inhibitory doses of estradiol. Inhibition was accompanied by increased pregnenolone accumulation, with a consequently augmented ratio of pregnenolone to progesterone. Moreover, in cell-free sonicates of granulosa cells, LY156758 directly inhibited 3 beta-hydroxysteroid dehydrogenase activity in a dose-dependent fashion, with half-maximal inhibition expressed at a drug concentration of 2.44 +/- 0.31 micrograms/ml compared with 85 +/- 19 ng/ml for estradiol. In addition, the combination of LY156758 and submaximally inhibitory doses of estradiol resulted in further suppression of 3 beta-hydroxysteroid dehydrogenase activity. The sustained stimulatory phase of estrogen action was also mimicked by moxestrol in a dose-dependent fashion. However, in contrast to its acute inhibitory effects, longer-term treatment with LY156758 slightly enhanced basal progesterone accumulation, and effectively antagonized estradiol's stimulatory actions. In summary, our results with moxestrol demonstrate that both the inhibitory and the stimulatory actions of estradiol are effectively mimicked by this synthetic estrogen agonist. Results with the selective anti-estrogen LY156758 indicate a small degree of intrinsic estrogen agonist activity (approx 4% that of estradiol), which is reflected by its acute and direct inhibition of 3 beta-hydroxysteroid dehydrogenase activity. However, under longer-term conditions in which estradiol's stimulation of progesterone production is expressed, LY156758 significantly antagonizes estradiol's trophic actions. Accordingly, we suggest that the acute suppressive effects of estradiol on progesterone production are mediated predominantly by direct inhibition of 3 beta-hydroxysteroid dehydrogenase activity, while delayed stimulatory effects are transduced via estrogen-receptor mechanisms.(ABSTRACT TRUNCATED AT 400 WORDS)
雌激素对猪颗粒细胞的孕酮生物合成具有双相作用，即最初的短暂抑制之后是延迟但持续的刺激。我们通过使用高选择性雌激素受体拮抗剂LY156758和合成雌激素激动剂莫昔司琼，测试了雌二醇受体在这些双相反应中的功能作用。莫昔司琼以剂量依赖性方式模拟了雌二醇的急性抑制作用（半数最大抑制剂量：54.3±25 ng/ml），但未被LY156758拮抗。相反，单独使用抗雌激素可显著抑制基础孕酮合成，并增强亚最大抑制剂量雌二醇的抑制作用。抑制伴随着孕烯醇酮积累增加，从而使孕烯醇酮与孕酮的比例增加。此外，在颗粒细胞的无细胞超声裂解物中，LY156758以剂量依赖性方式直接抑制3β-羟基类固醇脱氢酶活性，半数最大抑制浓度为2.44±0.31μg/ml，而雌二醇为85±19 ng/ml。此外，LY156758与亚最大抑制剂量的雌二醇联合使用导致3β-羟基类固醇脱氢酶活性进一步受到抑制。雌激素作用的持续刺激阶段也被莫昔司琼以剂量依赖性方式模拟。然而，与其急性抑制作用相反，LY156758长期治疗可轻微增强基础孕酮积累，并有效拮抗雌二醇的刺激作用。总之，我们使用莫昔司琼的结果表明，这种合成雌激素激动剂可有效模拟雌二醇的抑制和刺激作用。选择性抗雌激素LY156758的结果表明其具有一定程度的内在雌激素激动剂活性（约为雌二醇的4%），这反映在其对3β-羟基类固醇脱氢酶活性的急性和直接抑制上。然而，在长期条件下，当雌二醇刺激孕酮产生时，LY156758可显著拮抗雌二醇的营养作用。因此，我们认为雌二醇对孕酮产生的急性抑制作用主要通过直接抑制3β-羟基类固醇脱氢酶活性介导，而延迟刺激作用则通过雌激素受体机制传导。（摘要截于400字）
