Faltys G L, Convey E M, Short R E, Keech C A, Fogwell R L
J Anim Sci. 1987 May;64(5):1498-505. doi: 10.2527/jas1987.6451498x.
The effects of suckling on secretion of luteinizing hormone, cortisol and transcortin were investigated in anovulatory postpartum cows. On d 35 postpartum, calves were separated from 12 cows to prevent suckling and eight calves continued to suckle their dams ad libitum. Between 35 and 41 d postpartum, samples of jugular blood were collected every 15 min for two periods of 6 h/d. In non-suckled cows, frequency of pulses and basal luteinizing hormone increased but amplitude of pulses did not change. Concentrations of total cortisol in serum of cows were not altered during 3 d after weaning calves and did not differ among intervals before, during and after a suckling event. Affinity of transcortin for cortisol was not affected by postpartum interval or treatment. Capacity of transcortin to bind cortisol tended to increase after weaning. We found no evidence to support the hypothesis that suckling reduces binding capacity of transcortin or increases unbound cortisol. Differences in preovulatory secretion of luteinizing hormone between suckled and non-suckled cows could not be accounted for by differences in secretion of cortisol. In beef cows that are fed to satisfy requirements for energy and have average body condition, we conclude that negative modulation of luteinizing hormone by suckling is not mediated by cortisol.
研究了哺乳对产后不排卵奶牛促黄体生成素、皮质醇和皮质素转运蛋白分泌的影响。在产后第35天，将12头奶牛的犊牛与其分开以防止哺乳，另外8头犊牛继续随意 suckle 其母亲。在产后35至41天期间，每隔15分钟采集颈静脉血样，共采集两个时间段，每天6小时。在未哺乳的奶牛中，促黄体生成素脉冲频率和基础促黄体生成素增加，但脉冲幅度未改变。断奶犊牛后3天内，奶牛血清中总皮质醇浓度未改变，且在哺乳事件前、中、后的各时间段之间无差异。皮质素转运蛋白对皮质醇的亲和力不受产后间隔或处理的影响。断奶后，皮质素转运蛋白结合皮质醇的能力有增加的趋势。我们没有发现证据支持哺乳会降低皮质素转运蛋白结合能力或增加游离皮质醇的假设。哺乳和未哺乳奶牛促黄体生成素排卵前分泌的差异不能用皮质醇分泌的差异来解释。在满足能量需求且体况平均的肉牛中，我们得出结论，哺乳对促黄体生成素的负调节不是由皮质醇介导的。 （注：suckle 在此处应结合上下文准确理解其含义，推测是“哺乳”之意，但原英文表述此词使用不太规范，一般用 nurse 等更常用词）
