Martin G B, Scaramuzzi R J, Henstridge J D
J Endocrinol. 1983 Feb;96(2):181-93. doi: 10.1677/joe.0.0960181.
The effects of oestradiol-17 beta, androstenedione, progesterone and time of the year on the pulsatile secretion of LH were tested in ovariectomized Merino ewes (n = 32). The steroids were administered by small subcutaneous implants, and the LH pulses were observed in samples taken at intervals of 15 min for 12 h in spring 1979, autumn 1980 and spring 1980, seasons corresponding to successive periods of anoestrus, breeding season and anoestrus. During spring, oestradiol alone was able to reduce the frequency of the LH pulses, while progesterone, either alone or in combination with oestradiol, had little effect. During autumn, on the other hand, neither oestradiol nor progesterone could significantly reduce the frequency of the pulses when administered independently, whereas the combined treatment was very effective. Androstenedione had no significant effect on pulse frequency at either time of the year, either alone or in any combination with oestradiol and progesterone. The basal levels of LH, over which the pulses are superimposed, were reduced by oestradiol alone in both seasons. Progesterone alone had no consistent effects, but interacted significantly with oestradiol and this combined treatment maintained low basal levels most effectively at all times. Androstenedione had no significant effect. The amplitude of the pulses increased throughout the course of the experiment. Within seasons, the amplitudes were significantly higher in the presence of oestradiol and progesterone, but were not significantly affected by androstenedione. It was concluded that certain of the ovarian steroids exert negative feedback on the tonic secretion of LH primarily by reducing the frequency of the pulses, and that the changes in LH secretion attributable to season and phases of the oestrous cycle can be accounted for entirely by the responses of the hypothalamus to oestradiol and progesterone. The role of the androstenedione secreted by the ovary in the ewe remains obscure.
在切除卵巢的美利奴母羊（n = 32）中，测试了17β-雌二醇、雄烯二酮、孕酮以及一年中的时间对促黄体生成素（LH）脉冲式分泌的影响。通过小型皮下植入物给予这些类固醇，并在1979年春季、1980年秋季和1980年春季，每隔15分钟采集一次样本，观察12小时的LH脉冲，这些季节分别对应着连续的乏情期、繁殖季节和乏情期。在春季，单独使用雌二醇能够降低LH脉冲的频率，而孕酮单独使用或与雌二醇联合使用时影响不大。另一方面，在秋季，单独给予雌二醇或孕酮都不能显著降低脉冲频率，而联合治疗则非常有效。雄烯二酮在一年中的任何时候，单独使用或与雌二醇和孕酮联合使用，对脉冲频率均无显著影响。在两个季节中，单独使用雌二醇均可降低LH的基础水平，而LH脉冲叠加在该基础水平之上。孕酮单独使用没有一致的效果，但与雌二醇有显著相互作用，这种联合治疗在所有时间都能最有效地维持低基础水平。雄烯二酮没有显著影响。在整个实验过程中，脉冲幅度增加。在各个季节内，雌二醇和孕酮存在时脉冲幅度显著更高，但不受雄烯二酮的显著影响。得出的结论是，某些卵巢类固醇主要通过降低脉冲频率对LH的持续性分泌产生负反馈，并且发情周期的季节和阶段引起的LH分泌变化可以完全由下丘脑对雌二醇和孕酮的反应来解释。卵巢分泌的雄烯二酮在母羊中的作用仍不清楚。
