Clarke I J, Cummins J T, Jenkin M, Phillips D J
Medical Research Centre, Prince Henry's Hospital, Melbourne, Victoria, Australia.
J Endocrinol. 1989 Jul;122(1):127-34. doi: 10.1677/joe.0.1220127.
Two experiments were conducted with ovariectomized and hypothalamo-pituitary disconnected (HPD) ewes to ascertain the pattern of inputs, to the pituitary gland, of gonadotrophin-releasing hormone (GnRH) necessary for the full expression of an oestrogen-induced LH surge. The standard GnRH replacement to these sheep was to give pulses of 250 ng (i.v.) every 2h; at the onset of experimentation, pulses were given hourly. In experiment 1, groups of sheep (n = 7) were given an i.m. injection of 50 micrograms oestradiol benzoate, and after 10 h the GnRH pulse frequency or pulse amplitude was doubled. Monitoring of plasma LH concentrations showed that a doubling of pulse frequency produced a marked increase in baseline values, whereas a doubling of amplitude had little effect on the LH response. In a second experiment, ovariectomized HPD sheep that had received hourly pulses of GnRH for 16 h after an i.m. injection of oil or 50 micrograms oestradiol benzoate were given either a 'bolus' (2.25 micrograms GnRH) or a 'volley' (500 ng GnRH pulses 10 min apart for 30 min, plus a 500 ng pulse 15 min later). Both groups then received GnRH pulses (250 ng) every 30 min for the next 13 h. Oestrogen enhanced the LH responses to the GnRH treatments, and the amount of LH released was similar in ovariectomized HPD ewes given oestrogen plus bolus or volley GnRH treatments and ovariectomized hypothalamo-pituitary intact ewes given oestrogen. These results suggest that the oestrogen-induced LH surge is initiated by a 'signal' pattern of GnRH secretion from the hypothalamus.
进行了两项实验，以确定对于雌激素诱导的促黄体生成素（LH）峰完全表达所必需的促性腺激素释放激素（GnRH）输入垂体的模式，实验对象为卵巢切除和下丘脑 - 垂体分离（HPD）的母羊。对这些绵羊的标准GnRH替代方案是每2小时静脉注射250 ng脉冲；在实验开始时，每小时给予脉冲。在实验1中，给几组绵羊（n = 7）肌肉注射50微克苯甲酸雌二醇，10小时后将GnRH脉冲频率或脉冲幅度加倍。血浆LH浓度监测显示，脉冲频率加倍使基线值显著增加，而幅度加倍对LH反应影响不大。在第二项实验中，对肌肉注射油剂或50微克苯甲酸雌二醇后每小时接受GnRH脉冲16小时的卵巢切除HPD绵羊，给予“推注”（2.25微克GnRH）或“齐发”（相隔10分钟的500 ng GnRH脉冲，持续30分钟，随后15分钟后给予500 ng脉冲）。然后两组在接下来的13小时内每30分钟接受一次GnRH脉冲（250 ng）。雌激素增强了LH对GnRH治疗的反应，并且在接受雌激素加推注或齐发GnRH治疗的卵巢切除HPD母羊和接受雌激素的卵巢切除下丘脑 - 垂体完整母羊中释放的LH量相似。这些结果表明，雌激素诱导的LH峰是由下丘脑GnRH分泌的“信号”模式启动的。
