DEVELOPMENT OF ESTRADIOL-POSITIVE FEEDBACK ON LUTEINIZING-HORMONE RELEASE IN THE FEMALE RAT - A QUANTITATIVE STUDY
DEVELOPMENT OF ESTRADIOL-POSITIVE FEEDBACK ON LUTEINIZING-HORMONE RELEASE IN THE FEMALE RAT - A QUANTITATIVE STUDY
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DOI：
10.1210/endo-109-5-1404
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发表时间：
1981-01-01
期刊：
影响因子：
4.8
通讯作者：
OJEDA, SR
中科院分区：
文献类型：
--
作者：
ANDREWS, WW;MIZEJEWSKI, GJ;OJEDA, SR
进行实验以定量方式研究雌性大鼠中雌二醇（E2）正反馈对LH [促黄体生成激素]释放的发展。含有溶于玉米油（400 μ g/ml）中的E2的硅橡胶胶囊（20 mm长/100 g体重）在皮下植入时再现了第一次动情前期血清E2水平。在不同年龄的幼年大鼠中（20 - 32天）。当将类似的胶囊植入幼年大鼠（第10 - 18天）时，2天后测量的血清E2在12和14日龄大鼠中极高（比第一次发情前水平高4 - 6倍），此后下降，因此在16 - 20日龄大鼠中，水平仅为发情前值的2倍。血清中α-胎蛋白在第12 - 28天之间显著降低，正常和植入物产生的血清E2水平都抑制了蛋白滴度的下降。计算α-雌二醇的总E2结合能力胎儿蛋白的研究表明，除了与这种蛋白结合外，还有其他因素导致E2在幼年大鼠血清中的持续存在。LH峰不能诱导在12或14日龄大鼠48小时E2脉冲，尽管存在大量的游离E2，产生深刻的负反馈效应。在第16 - 20天之间，只有至少2倍于第一次发情前值的E2水平才能有效诱导LH峰。在第22 - 34天之间，血清E2水平引起LH激增，与第一次发情前期期间观察到的非常相似。到第26 - 28天，LH峰的曲线与第一次排卵前峰的曲线难以区分。从第26天开始，除了48 h E2脉冲引起的LH峰外，E2植入后第二天还出现了较早的LH峰。到第30天，早期LH峰牢固建立，晚期峰不再明显。雌鼠E_2正反馈的形成包括4个阶段：第一阶段，在第16天之前，LH释放系统的峰机制尚未形成，第二阶段，在第16 - 20天之间，E_2水平需要达到发情前期的2倍才能激活LH峰机制;第三阶段，在幼年期开始时开始（约第20 - 22天），其中LH峰机制响应于排卵前量级的E2水平;和第IV阶段，其开始于第26 - 28天左右，其中暴露于排卵前量级的E2水平24小时足以引起LH峰。
Experiments were conducted to study, in a quantitative manner, the development of estradiol (E2)-positive feedback on LH [luteinizing hormone] release in the female rat. A Silastic capsule (20 mm in length/100 g body wt) containing E2 dissolved in corn oil (400 .mu.g/ml) reproduced 1st proestrous levels of serum E2 when implanted s.c. in juvenile rats of different ages (days 20-32). When similar capsules were implanted in infantile rats (days 10-18), serum E2, measured 2 days later, was extremely elevated in 12- and 14-day-old rats (4-6 times higher than 1st proestrous levels), declining therafter so that in 16- to 20-day-old rats, the levels were only 2-fold > proestrous values. Serum levels of .alpha.-fetoprotein decreased markedly between days 12-28, and both normal and implant-produced serum E2 levels paralleled the decline in the protein titers. Calculation of the total E2 binding capacity of .alpha.-fetoprotein indicated that in addition to binding to this protein, there are additional factors responsible for the persistence of E2 in the serum of infantile rats. An LH surge could not be induced in 12- or 14-day-old rats by a 48 h E2 pulse, despite the presence of substantial amounts of free E2, which exerted profound negative feedback effects. Between days 16-20, only E2 levels that were at least 2-fold > 1st proestrous values were effective in inducing a LH surge. Between days 22-34, a LH surge was elicited by serum E2 levels very similar to those seen during the 1st proestrus. By days 26-28, the profile of the LH surge was indistinguishable from that of the 1st preovulatory surge. Starting on day 26, and in addition to the LH surge elicited by the 48 h E2 pulse, an earlier surge occurred on the next day after E2 implantation. By day 30, the early LH surge became firmly established, and the late surge was no longer apparent. In the female rat, the development of E2-positive feedback comprises 4 phases: phase I, before day 16, in which the surge mechanism of the LH releasing system is not developed; phase II, between days 16-20, in which E2 levels twice as high as those of 1 proestrus are necessary to activate the LH surge mechanism; phase III, which is initiated at the beginning of the juvenile period (.apprx. days 20-22) and in which the LH surge mechanism responds to E2 levels of preovulatory magnitude; and phase IV, which begins around days 26-28 and in which a 24 h exposure to E2 levels of prevulatory magnitude is sufficient to elicit a LH surge.