Chronic elevation of estradiol in young ovariectomized rats causes aging-like loss of steroid-induced luteinizing hormone surges.
Chronic elevation of estradiol in young ovariectomized rats causes aging-like loss of steroid-induced luteinizing hormone surges.
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年轻的卵巢切除大鼠中雌二醇的慢性升高会导致类固醇引起的黄体生成激素激增的衰老样损失。
DOI：
10.1095/biolreprod64.2.684
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发表时间：
2001
影响因子：
3.6
通讯作者：
Legan,SJ
中科院分区：
文献类型：
--
作者：
Tsai,HW;Legan,SJ
本研究旨在验证一种假设，即中年持续发情（PE）大鼠在雌二醇和黄体酮的刺激作用下，黄体生成素（LH）激增的损失可能是由循环雌二醇的慢性升高引起的。五组定期循环的年轻大鼠在卵巢切除术后立即（第0天）植入sc雌二醇。为了测定黄体生成素激增，在1200-1900小时之间，在以下时间中的一个从五组中每小时采集血液样本：3天，或1、2、4或8周后。第二天，在1200 h注射黄体酮（0.5 mg/100 g BW）或玉米油，取样品。雌二醇诱导的黄体生成素激增的发生率和幅度在雌二醇治疗的前2周内下降，之后没有出现激增。黄体酮增加了雌二醇诱导的LH激增的发生率和幅度，从而延缓了它们的消失。这些结果支持了我们的假设，并证明雌二醇和黄体酮对黄体生成素激增的刺激作用在暴露于雌二醇后随着时间的推移而逐渐减弱。因此，长期接受雌二醇治疗的年轻大鼠可能是研究黄体生成素激增在中年PE高雌激素状态下被消除的机制的有用模型。
This study was designed to test the hypothesis that the loss of LH surges in response to the stimulatory actions of estradiol and progesterone in middle-aged, persistent-estrous (PE) rats may be caused by chronic elevations in circulating estradiol. Five groups of regularly cycling young rats received an s.c. estradiol implant immediately after ovariectomy (Day 0). For determination of LH surges, blood samples were collected hourly between 1200–1900 h from each of the five groups at one of the following times: 3 days, or 1, 2, 4, or 8 wk later. On the next day, either progesterone (0.5 mg/100 g BW) or corn oil was injected s.c. at 1200 h, and samples were obtained as before. Incidence and amplitude of estradiol-induced LH surges decreased during the first 2 wk of estradiol treatment, after which no surges occurred. Progesterone enhanced the incidence and amplitude of estradiol-induced LH surges thus delaying their disappearance. These results support our hypothesis and demonstrate that the stimulatory actions of estradiol and progesterone on the LH surge sequentially diminish with time after exposure to estradiol in young rats. Thus, young rats chronically treated with estradiol may be a useful model for studying the mechanisms whereby LH surges are abolished in middle age during the hyperestrogenic state of PE.