Baldwin D M, Srivastava P S, Krummen L A
Department of Reproduction, School of Veterinary Medicine, University of California, Davis 95616.
Biol Reprod. 1991 Jun;44(6):1040-50. doi: 10.1095/biolreprod44.6.1040.
Previous in vivo studies from our laboratory suggested that glucocorticoids antagonize estrogen-dependent actions on LH secretion. This study investigated whether corticosterone (B) may have similar actions on gonadotropin biosynthesis and secretion in vitro. Enzymatically dispersed anterior pituitary cells from adult female rats were cultured for 48 h in alpha-modified Eagle's medium containing 10% steroid-free horse serum with or without 0.5 nM estradiol (E2). The cells were then cultured for 24 h with or without B in the presence or absence of E2. To evaluate hormone release, 5 x 10(5) cells were incubated with varying doses of GnRH (0, 10(-11)-10(-7) M) or pulsatile GnRH (10(-9) M; 20 min/h) for 4 h. Cell and medium LH and FSH were measured by RIA. To evaluate LH biosynthesis, 5 x 10(6) cells were incubated for an additional 24 h with 10(-10) M GnRH, 60 microCi 3H-glucosamine (3H-Gln), 20 microCi 35S-methionine (35S-Met), and the appropriate steroid hormones. Radiolabeled precursor incorporation into LH subunits was determined by immunoprecipitation, followed by SDS-PAGE. Continuous exposure to GnRH stimulated LH release in a dose-dependent manner, and this response was enhanced by E2. B by itself had no effect on LH release, but inhibited LH secretion in E2-primed cells at low concentrations of GnRH (10(-10) M or less). Total LH content was not altered by GnRH or steroid treatment. Similar effects of B were observed in cells that were given a pulsatile GnRH stimulus. In contrast to LH, E2 or B enhanced GnRH-stimulated FSH release at the higher doses of GnRH, while the combination of E2 and B increased basal and further augmented GnRH-stimulated release. Total FSH content was also increased in the presence of B, but not E2 alone, and was further augmented in cells treated with both steroids. There were no effects of the steroids on the magnitude of FSH release in response to GnRH pulses, but the cumulative release of FSH was greater in the E2 + B group compared to controls, indicating an increased basal release. Independent of E2, B suppressed the incorporation of 3H-Gln into LH by more than 50% of control, with only subtle effects on the incorporation of 35S-Met.(ABSTRACT TRUNCATED AT 400 WORDS)
我们实验室之前的体内研究表明，糖皮质激素可拮抗雌激素对促黄体生成素（LH）分泌的依赖性作用。本研究调查了皮质酮（B）在体外对促性腺激素生物合成和分泌是否可能具有类似作用。将成年雌性大鼠经酶分散的垂体前叶细胞在含有10%无类固醇马血清的α-改良伊格尔培养基中培养48小时，添加或不添加0.5 nM雌二醇（E2）。然后，在有或无E2存在的情况下，将细胞与B一起或不与B一起再培养24小时。为评估激素释放，将5×10⁵个细胞与不同剂量的促性腺激素释放激素（GnRH，0、10⁻¹¹ - 10⁻⁷ M）或脉冲式GnRH（10⁻⁹ M；20分钟/小时）孵育4小时。通过放射免疫分析法（RIA）测量细胞和培养基中的LH和促卵泡生成素（FSH）。为评估LH生物合成，将5×10⁶个细胞与10⁻¹⁰ M GnRH、60微居里³H-葡糖胺（³H-Gln）、20微居里³⁵S-甲硫氨酸（³⁵S-Met）以及适当的类固醇激素再孵育24小时。通过免疫沉淀法，随后进行十二烷基硫酸钠-聚丙烯酰胺凝胶电泳（SDS-PAGE），测定放射性标记前体掺入LH亚基的情况。持续暴露于GnRH以剂量依赖性方式刺激LH释放，且该反应被E2增强。B本身对LH释放无影响，但在低浓度GnRH（10⁻¹⁰ M或更低）时抑制E2预处理细胞中的LH分泌。GnRH或类固醇处理未改变LH总含量。在给予脉冲式GnRH刺激的细胞中也观察到B的类似作用。与LH不同，在较高剂量的GnRH时，E2或B增强GnRH刺激的FSH释放，而E2和B的组合增加基础FSH释放并进一步增强GnRH刺激的释放。在有B存在时FSH总含量也增加，但单独E2时不增加，且在两种类固醇处理的细胞中进一步增加。类固醇对GnRH脉冲刺激引起的FSH释放幅度无影响，但与对照组相比，E2 + B组中FSH的累积释放更大，表明基础释放增加。与E2无关，B将³H-Gln掺入LH的量抑制至对照的50%以上，而对³⁵S-Met的掺入仅有细微影响。（摘要截断于400字）
