Turgeon J L, Waring D W
Endocrinology. 1981 Feb;108(2):413-9. doi: 10.1210/endo-108-2-413.
During the rat estrous cycle there are marked changes in the concentrations of serum 17 beta-estradiol (E2) and progesterone. The objective of the present study was to examine the acute effects of E2 and progesterone on isolated pituitaries obtained at 1230 h at each stage of the 4-day cycle. At time zero, single quartered anterior pituitaries were placed in a chamber and superfused at 0.5 ml/min with medium 199 with or without steroids for 360 min; sequential 10-min effluent samples were collected. LHRH (10 ng/ml) was administered as two successive 10-min pulses at 120 and 240 min. The proestrous and the diestrous-II pituitaries in vitro exhibited the characteristic LHRH self-priming response: an increased LH secretory response to a second pulse of LHRH in both the absence and presence of steroids in the superfusion medium; however, the magnitude of the response to the initial pulse of LHRH was reduced significantly when E2 (50 pg/ml) was present. The presence of progesterone (50 ng/ml) resulted in a marked augmentation of the LH secretory response to the first pulse of LHRH; when both E2 and progesterone were included in the superfusion medium, the stimulatory effect of progesterone was reduced. The progesterone augmentation of LHRH-induced LH secretion was present after 60 min of steroid exposure in vitro but was not demonstrable after only 10 min of exposure. Cycloheximide inhibited the progesterone augmentation and the LHRH self-priming without affecting the LH secretory response to the initial LHRH pulse in the absence of steroid. Progesterone augmentation was not observed on estrus and diestrous-I. The presence of E2 in the medium, however, resulted in a significant decrease in the response to the first pulse of LHRH for pituitaries from either estrus or diestrous-I. These data 1) demonstrate that E2 by itself suppresses LHRH-induced LH secretion by the proestrous pituitary and 2) provide proof for a direct stimulatory action of progesterone, in the absence of E2, on the proestrous pituitary and suggest a positive feedback role for progesterone during the preovulatory LH surge. (Endocrinology 108: 413, 1981)
在大鼠发情周期中，血清17β-雌二醇（E2）和孕酮的浓度会发生显著变化。本研究的目的是检测E2和孕酮对在4天周期各阶段的1230时获取的离体垂体的急性影响。在时间零点，将单个切成四等分的垂体前叶放入一个腔室中，以0.5毫升/分钟的速度用含或不含类固醇的199培养基进行360分钟的灌流；收集连续的10分钟流出液样本。在120分钟和240分钟时，以两个连续的10分钟脉冲形式给予促性腺激素释放激素（LHRH，10纳克/毫升）。动情前期和动情后期-II的离体垂体表现出典型的LHRH自启动反应：在灌流培养基中无论有无类固醇，对LHRH的第二个脉冲的促黄体生成素（LH）分泌反应均增加；然而，当存在E2（50皮克/毫升）时，对LHRH初始脉冲的反应幅度显著降低。孕酮（50纳克/毫升）的存在导致对LHRH第一个脉冲的LH分泌反应显著增强；当灌流培养基中同时包含E2和孕酮时，孕酮的刺激作用减弱。在体外暴露于类固醇60分钟后出现了孕酮增强LHRH诱导的LH分泌的现象，但仅暴露10分钟后未观察到。放线菌酮抑制了孕酮增强作用和LHRH自启动反应，而在无类固醇的情况下不影响对初始LHRH脉冲的LH分泌反应。在发情期和动情前期-I未观察到孕酮增强作用。然而，培养基中E2的存在导致来自发情期或动情前期-I的垂体对LHRH第一个脉冲的反应显著降低。这些数据1）表明E2自身可抑制动情前期垂体对LHRH诱导的LH分泌，2）证明在无E2的情况下孕酮对动情前期垂体有直接刺激作用，并提示孕酮在排卵前LH峰期间起正反馈作用。（《内分泌学》108：413，1981年）
