Role of gonadotropins and progesterone in determining the preovulatory estradiol rise in the ewe.
Role of gonadotropins and progesterone in determining the preovulatory estradiol rise in the ewe.
复制标题
促性腺激素和黄体酮在确定母羊排卵前雌二醇升高中的作用。
DOI：
10.1095/biolreprod25.1.134
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发表时间：
1981
影响因子：
3.6
通讯作者：
Karsch,FJ
中科院分区：
文献类型：
--
作者：
Goodman,RL;ReichertJr,LE;Legan,SJ;Ryan,KD;Foster,DL;Karsch,FJ
通过模拟这些变化，单独或组合，在季节性发情动物的卵泡期增加LH和孕酮的减少，以确定排卵前雌二醇上升的母羊的贡献进行了检查。在此测试之前，每只母羊用含有孕酮的Silastic植入物预处理15天，以产生人工黄体期。然后将植入物取出或留在原位，并输注纯化的绵羊LH以模拟发情周期卵泡期期间观察到的平均血清LH浓度的逐渐增加。如果不给予LH，无论是否停用孕酮，雌二醇的浓度都保持较低和恒定。当黄体生成素输注后，孕酮撤出（n = 8），血清雌二醇显着增加，从1至5 pg/ml的结果。其中4只母羊出现LH峰，诱导排卵并形成功能性黄体。在这些母羊，雌二醇急剧下降4小时内的LH峰值。在其他4只动物中，未发生LH峰，雌二醇保持升高直至输注结束。当黄体期孕酮浓度维持不变时，LH输注可使血清雌二醇升高，但其作用显著低于停药时LH所产生的作用（P<0.01），这些数据表明，在母羊中，卵泡期雌二醇的升高是由持续增加的LH紧张性分泌所驱动的，并由排卵前LH峰所终止。黄体溶解时孕酮的下降可能以两种方式促进雌二醇的升高：1）它允许必需的LH紧张性分泌的增加; 2）它增加了卵泡对LH增加的反应。最后，通过证明卵巢的不动情母羊可以产生一个雌二醇上升，在卵泡期LH的增量，这些研究提供了重要的支持的假设，季节性不动情的主要原因是缺乏持续上升的紧张性LH分泌。
The contributions of the follicular phase increase in LH and the decrease in progesterone to the determination of the preovulatory estradiol rise in the ewe were examined by mimicking these changes, separately or in combination, in seasonally anestrous animals. Prior to this test, each ewe was pretreated for 15 days with Silastic implants containing progesterone to produce an artificial luteal phase. The implants were then either removed or left in place, and purified ovine LH was infused to simulate the progressive increase in mean serum LH concentrations seen during the follicular phase of the estrous cycle. If LH was not given, the concentration of estradiol remained low and constant, whether or not progesterone was withdrawn. When LH was infused after progesterone withdrawal (n = 8), a significant increase in serum estradiol from 1 to 5 pg/ml resulted. Four of these ewes had an LH surge, which induced ovulation and formation of functional corpora lutea. In these ewes, estradiol fell precipitously within 4 h of the LH peak. In the other four animals, no LH surge occurred and estradiol remained elevated until the end of the infusion. When a luteal phase progesterone concentration was maintained, LH infusion produced an elevation in serum estradiol, but the response was significantly less (P<0.01) than that produced by LH when progesterone was withdrawn.These data suggest that, in the ewe, the follicular phase estradiol rise is driven by the sustained increase in tonic LH secretion and is terminated by the preovulatory LH surge. The fall in progesterone at luteolysis probably contributes to the estradiol rise in 2 ways: 1) it allows the requisite increase in tonic LH secretion; and 2) it increases the response of the follicle to this LH increase. Finally, by demonstrating that the ovary of the anestrous ewe can produce an estradiol rise in response to a follicular phase increment in LH, these studies provide important support for the hypothesis that a primary cause of seasonal anestrus is the absence of a sustained rise in tonic LH secretion.