Lacroix A, Pelletier J
Acta Endocrinol (Copenh). 1979 Aug;91(4):719-29. doi: 10.1530/acta.0.0910719.
LH and testosterone release after LH-RH treatment was studied in male calves from 1 week to 8 months of age. Total LH release, LH peak values and duration of the discharge increased from 1 week to 4 months of age by 406, 453 and 110%, respectively. Significant decreases of 54, 48 and 24% were observed at 6 months of age compared to 4 months of age. This was followed by steep increases in those variables of 344, 129 and 69% at 8 months compared to 4 months. A testosterone response following an LH increase was first seen at 4 months of age when a weak discharge occurred in 2 out of 5 calves. In older calves strong and LH-correlated testosterone responses were always observed. In a second experiment the LH response to LH-RH was studied in 6 months old calves castrated 2 months previously. The total LH response was 61% greater than in intact controls. When animals were castrated and pre-treated briefly with testosterone propionate the response was increased by 183% and the time to reach the LH peak was increased by 360%. From these and other results a synthesis of endocrine events during the first year of life is proposed. In particular it seems that the period between 4 and 8 months of age is crucial since interactions between steroid feedback and pituitary sensitivity to LH-RH change and eventually reach an equilibrium.
研究了1周龄至8月龄雄性犊牛经促黄体生成素释放激素（LH-RH）处理后的促黄体生成素（LH）和睾酮释放情况。从1周龄到4月龄，LH的总释放量、LH峰值和释放持续时间分别增加了406%、453%和110%。与4月龄相比，6月龄时这些指标显著下降，降幅分别为54%、48%和24%。随后，与4月龄相比，8月龄时这些变量急剧增加，增幅分别为344%、129%和69%。LH升高后睾酮的反应在4月龄时首次出现，当时5头犊牛中有2头发生了微弱的释放。在年龄较大的犊牛中，总是观察到强烈的且与LH相关的睾酮反应。在第二项实验中，研究了2个月前阉割的6月龄犊牛对LH-RH的LH反应。LH的总反应比完整对照组大61%。当动物被阉割并用丙酸睾酮短暂预处理时，反应增加了183%，达到LH峰值的时间增加了360%。根据这些及其他结果，提出了生命第一年内分泌事件的综合情况。特别是，4至8月龄这段时间似乎至关重要，因为类固醇反馈与垂体对LH-RH的敏感性之间的相互作用发生变化，最终达到平衡。
