Menon M, Peegel H, Katta V
Am J Obstet Gynecol. 1985 Feb 15;151(4):534-40. doi: 10.1016/0002-9378(85)90284-4.
In order to investigate the mechanism by which 17 beta-estradiol potentiates the action of gonadotropin-releasing hormone on the anterior pituitary in vitro, cultured pituitary cells from immature female rats were used as the model system. Cultures exposed to estradiol at concentrations ranging from 10(-10) to 10(-6) mol/L exhibited a significant augmentation of luteinizing hormone release in response to a 4-hour gonadotropin-releasing hormone (10 mumol/L) challenge at a dose of 10(-9) mol/L compared to that of control cultures. The estradiol augmentation of luteinizing hormone release was also dependent on the duration of estradiol exposure. When these cultures were incubated with tritium-labeled L-leucine, an increase in incorporation of radiolabeled amino acid into total proteins greater than that in controls was observed. A parallel stimulatory effect of estradiol on iodine 125-labeled D-Ala6 gonadotropin-releasing hormone binding was observed. Cultures incubated with estradiol at different concentrations and various lengths of time showed a significant increase in gonadotropin-releasing hormone binding capacity and this increase was abrogated by cycloheximide. Analysis of the binding data showed that the increase in gonadotropin-releasing hormone binding activity was due to a change in the number of gonadotropin-releasing hormone binding sites rather than a change in the affinity. These results suggest that (1) estradiol treatment increases the number of pituitary receptors for gonadotropin-releasing hormone, (2) the augmentary effect of estradiol on luteinizing hormone release at the pituitary level might be mediated, at least in part, by the increase in the number of binding sites of gonadotropin-releasing hormone, and (3) new protein synthesis may be involved in estradiol-mediated gonadotropin-releasing hormone receptor induction.
为了研究17β-雌二醇增强促性腺激素释放激素对体外培养的未成熟雌性大鼠垂体前叶作用的机制，以体外培养的未成熟雌性大鼠垂体细胞作为模型系统。与对照培养物相比，暴露于浓度范围为10(-10)至10(-6)mol/L雌二醇的培养物，在受到剂量为10(-9)mol/L的促性腺激素释放激素（10μmol/L）刺激4小时后，促黄体生成素释放显著增加。促黄体生成素释放的雌二醇增强作用也取决于雌二醇暴露的持续时间。当这些培养物与氚标记的L-亮氨酸一起孵育时，观察到放射性标记氨基酸掺入总蛋白的量比对照增加。观察到雌二醇对125I标记的D-Ala6促性腺激素释放激素结合有类似的刺激作用。用不同浓度和不同时间的雌二醇孵育的培养物显示促性腺激素释放激素结合能力显著增加，并且这种增加被环己酰亚胺消除。结合数据分析表明，促性腺激素释放激素结合活性的增加是由于促性腺激素释放激素结合位点数量的变化而不是亲和力的变化。这些结果表明：（1）雌二醇处理增加了垂体促性腺激素释放激素受体的数量；（2）雌二醇在垂体水平对促黄体生成素释放的增强作用可能至少部分是由促性腺激素释放激素结合位点数量的增加介导的；（3）新的蛋白质合成可能参与了雌二醇介导的促性腺激素释放激素受体的诱导。
