Lin Y W, Schuetz A W
Gen Comp Endocrinol. 1985 Jun;58(3):421-35. doi: 10.1016/0016-6480(85)90115-7.
Previous studies demonstrated that estrogen inhibited frog pituitary homogenate (FPH) and progesterone-induced oocyte maturation. In order to determine whether estrogen interfered with intrafollicular progesterone synthesis, experiments were designed to study the effect of exogenous estrogen (estradiol-17 beta) on FPH-induced progesterone production in amphibian (Rana pipiens) ovarian follicles cultured in vitro. Intrafollicular progesterone concentrations were monitored directly using radioimmunoassay and the occurrence of germinal vesicle breakdown (GVBD) was used as a biological indicator of the action of steroids on oocyte maturation. FPH elicited a rapid and dramatic increase in follicular progesterone concentration (1000-3000 pg per follicle) which preceded germinal vesicle breakdown. Addition of estrogen to the culture medium inhibited FPH-induced progesterone production and the accompanying GVBD in a dose-dependent fashion. The presence of estrogen did not enhance the degradation of preloaded progesterone, suggesting estrogen impeded progesterone synthesis rather than enhanced progesterone metabolism. The temporal relationship between estrogen and FPH interaction was assessed by varying the relative time of hormone addition, after which intrafollicular progesterone concentration and GVBD were monitored. Progesterone production and GVBD were drastically inhibited when estrogen was added before or simultaneously with FPH. However, when addition of estrogen was delayed until after FPH simulation, a progressive loss of the inhibitory effect of the steroid on progesterone accumulation and GVBD was observed. Thus, the estrogen-sensitive phase was confined to the early portion of FPH stimulation. Continuous presence of estrogen in the culture system was not required to inhibit FPH-induced events. A short exposure (15 min) of follicles to estrogen was sufficient to inhibit oocyte maturation, whereas progesterone synthesis was not significantly affected. With longer exposure, however, FPH-induced progesterone production was impeded. Washing estrogen-treated follicles did not reverse the inhibitory effect of estrogen, however the follicles remained responsive to exogenous progesterone stimulation and exhibited GVBD. Results suggest that the inhibitory effects of estrogen on FPH action and progesterone production were not reversible under the in vitro culture conditions. To determine whether specific follicular components were involved in estrogen inhibition, progesterone production was assessed following selective removal of different follicle components by microdissection prior to being treated with FPH and estrogen.(ABSTRACT TRUNCATED AT 400 WORDS)
先前的研究表明，雌激素可抑制蛙垂体匀浆（FPH）和孕酮诱导的卵母细胞成熟。为了确定雌激素是否干扰卵泡内孕酮的合成，设计了实验来研究外源性雌激素（17β-雌二醇）对体外培养的两栖动物（豹蛙）卵巢卵泡中FPH诱导的孕酮产生的影响。使用放射免疫分析法直接监测卵泡内孕酮浓度，并将生发泡破裂（GVBD）的发生用作类固醇对卵母细胞成熟作用的生物学指标。FPH引起卵泡孕酮浓度迅速且显著升高（每个卵泡1000 - 3000 pg），这发生在生发泡破裂之前。向培养基中添加雌激素以剂量依赖的方式抑制FPH诱导的孕酮产生及伴随的GVBD。雌激素的存在并未增强预先加载的孕酮的降解，这表明雌激素阻碍孕酮合成而非增强孕酮代谢。通过改变激素添加的相对时间来评估雌激素与FPH相互作用的时间关系，之后监测卵泡内孕酮浓度和GVBD。当在FPH之前或同时添加雌激素时，孕酮产生和GVBD受到显著抑制。然而，当雌激素添加延迟至FPH刺激之后时，观察到类固醇对孕酮积累和GVBD的抑制作用逐渐丧失。因此，雌激素敏感阶段局限于FPH刺激的早期部分。培养系统中不需要持续存在雌激素来抑制FPH诱导的事件。卵泡短时间暴露（15分钟）于雌激素足以抑制卵母细胞成熟，而孕酮合成未受到显著影响。然而，暴露时间更长时，FPH诱导的孕酮产生受到阻碍。冲洗经雌激素处理的卵泡并未逆转雌激素的抑制作用，不过卵泡对外源性孕酮刺激仍有反应并表现出GVBD。结果表明，在体外培养条件下，雌激素对FPH作用和孕酮产生的抑制作用是不可逆的。为了确定特定的卵泡成分是否参与雌激素抑制作用，在经FPH和雌激素处理之前，通过显微解剖选择性去除不同的卵泡成分后评估孕酮产生。（摘要截短至400字）
