Montgomery G W, Martin G B, Pelletier J
J Reprod Fertil. 1985 Jan;73(1):173-83. doi: 10.1530/jrf.0.0730173.
Two experiments were conducted in Ile-de-France ewes to study changes in pulsatile LH secretion in ewes ovariectomized during anoestrus or during the midluteal phase of the oestrous cycle. In Exp. 1, blood samples were taken every 20 min for 12 h the day before ovariectomy (Day 0). After ovariectomy, samples were taken every 10 min for 6 h (10 ewes per group), on Days 1, 3, 7 and 15. In Exp. 2 samples were taken every 10 min for 6 h (10 ewes per group) on Days 7, 15, 30, 60, 90, 120, 150 and 180 after ovariectomy. Further samples were taken (5 ewes per group) at 9 and 12 months after ovariectomy. There were significant interactions between season and day of sampling for the interval between LH pulses in both experiments. LH pulse frequency increased within 1 day of ovariectomy and the increase was more rapid during the breeding season. There were clear seasonal differences in pulse frequency in Exp. 2. Compared with ewes ovariectomized in anoestrus, pulse frequency was significantly higher for ewes ovariectomized in the breeding season, from Day 7 until Day 120. Once pulse frequency had increased in ewes about the time of the normal breeding season, pulse frequency remained high and subsequent seasonal changes were greatly reduced. Pulse amplitude increased immediately after ovariectomy to reach a maximum on Day 7 and there were no differences between season of ovariectomy in the initial changes in amplitude. In Exp. 2, changes in amplitude followed changes in pulse interval and there was a significant interaction between season and day of sampling. There were no significant effects of season on nadir LH concentrations which increased throughout the duration of the experiments. These results show that, in ovariectomized ewes, LH pulse frequency observed on a given day depends on time after ovariectomy, season at the time of sampling and on previous exposure of ewes to stimulatory effects of season. The direct effects of season on LH pulse frequency and seasonal changes in sensitivity to steroid feedback may contribute to control of the breeding season and their relative contributions to the beginning and end of the breeding season may differ.
在法兰西岛母羊身上进行了两项实验，以研究在发情周期的乏情期或黄体中期进行卵巢切除的母羊中促黄体生成素（LH）脉冲式分泌的变化。在实验1中，在卵巢切除术前一天（第0天），每20分钟采集一次血样，持续12小时。卵巢切除术后，在第1、3、7和15天，每10分钟采集一次血样，持续6小时（每组10只母羊）。在实验2中，在卵巢切除术后第7、15、30、60、90、120、150和180天，每10分钟采集一次血样，持续6小时（每组10只母羊）。在卵巢切除术后9个月和12个月时，进一步采集血样（每组5只母羊）。在两项实验中，LH脉冲间隔的采样季节和采样日之间均存在显著交互作用。LH脉冲频率在卵巢切除术后1天内增加，且在繁殖季节增加更为迅速。在实验2中，脉冲频率存在明显的季节性差异。与在乏情期进行卵巢切除的母羊相比，在繁殖季节进行卵巢切除的母羊从第7天到第120天的脉冲频率显著更高。一旦母羊在正常繁殖季节前后的脉冲频率增加，脉冲频率就会保持在较高水平，随后的季节性变化会大大减少。卵巢切除术后，脉冲幅度立即增加，在第7天达到最大值，卵巢切除季节在幅度的初始变化方面没有差异。在实验2中，幅度变化跟随脉冲间隔变化，采样季节和采样日之间存在显著交互作用。季节对LH最低浓度没有显著影响，在整个实验过程中LH最低浓度持续增加。这些结果表明，在卵巢切除的母羊中，某一天观察到的LH脉冲频率取决于卵巢切除后的时间、采样时的季节以及母羊先前对季节刺激效应的暴露情况。季节对LH脉冲频率的直接影响以及对类固醇反馈敏感性的季节性变化可能有助于控制繁殖季节，它们对繁殖季节开始和结束的相对贡献可能有所不同。
