Chamley W A, Adams N R, Hooley R D, Carson R
Aust J Biol Sci. 1981;34(2):239-44. doi: 10.1071/bi9810239.
Plasma luteinizing hormone (LH) concentrations were measure in normal Merino ewes and in Merino ewes with lowered fertility which had resulted from prolonged grazing of Trifolium subterraneum L. cv. Dinninup. During the anoestrous season, LH was measured at frequent intervals before and following administration of oestradiol-17 beta or gonadotropin releasing hormone (GnRH), and around the time of spontaneous oestrus. All ewes responded to GnRH treatment and there were no differences between the two groups in terms of the amount of LH released or the time to reach maximal plasma hormone concentration. Comparable proportions of ewes from both groups responded to oestradiol-17 beta treatment with LH levels showing initially a negative feedback response (i.e. suppression to approximately 80% of pretreatment levels) followed by positive feedback response. During the positive feedback phase, the quantity of LH which was released was comparable in both groups; however, the time interval over which this hormone was secreted was significantly shorter for clover-infertile ewes (P less than 0.05). During the anoestrous season the mean LH level was lower in normal ewes than in clover-infertile ewes [0.45 +/- 0.41 (n = 32) versus 0.82 +/- 0.73 (n = 48 ng/ml, P less than 0.01]. In the oestrous season the mean LH level for normal ewes rose to 1.23 +/- 0.65 ng/ml (n = 76) but there was no change for the clover-infertile ewes (0.77 +/- 0.59 ng/ml, n = 73). These experiments indicate that in the clover-infertile ewe LH concentration remains static throughout the breeding and non-breeding seasons but the results suggest that this altered endocrine status in not due to any differing level of sensitivity to negative feedback effects of oestradiol-17 beta as compared with normal ewes.
在正常美利奴母羊以及因长期放牧三叶草（Trifolium subterraneum L. cv. Dinninup）而导致繁殖力下降的美利奴母羊中，测定了血浆促黄体生成素（LH）浓度。在乏情季节，在给予17β-雌二醇或促性腺激素释放激素（GnRH）之前和之后，以及在自然发情期前后，频繁测定LH。所有母羊对GnRH治疗均有反应，两组之间在释放的LH量或达到最大血浆激素浓度的时间方面没有差异。两组中相当比例的母羊对17β-雌二醇治疗有反应，LH水平最初呈现负反馈反应（即抑制至预处理水平的约80%），随后是正反馈反应。在正反馈阶段，两组释放的LH量相当；然而，三叶草不孕母羊分泌这种激素的时间间隔明显更短（P<0.05）。在乏情季节，正常母羊的平均LH水平低于三叶草不孕母羊[0.45±0.41（n = 32）对0.82±0.73（n = 48 ng/ml，P<0.01]。在发情季节，正常母羊的平均LH水平升至1.23±0.65 ng/ml（n = 76），但三叶草不孕母羊没有变化（0.77±0.59 ng/ml，n = 73）。这些实验表明，在三叶草不孕母羊中，LH浓度在整个繁殖和非繁殖季节保持稳定，但结果表明，与正常母羊相比，这种内分泌状态的改变并非由于对17β-雌二醇负反馈作用的敏感性存在任何差异。
