McNeilly A S, Crow W J, Fraser H M
MRC Reproductive Biology Unit, University of Edinburgh, UK.
J Reprod Fertil. 1992 Nov;96(2):865-74. doi: 10.1530/jrf.0.0960865.
Progesterone secretion has been observed to be episodic in the late luteal phase of the oestrous cycle of ewes and is apparently independent of luteinizing hormone (LH). This study investigated the effects of suppressing the pulsatile release of LH in the early or late luteal phase on the episodic secretion of progesterone. Six Scottish Blackface ewes were treated i.m. with 1 mg kg-1 body weight of a potent gonadotrophin-releasing hormone (GnRH) antagonist on either day 4 or day 11 of the luteal phase. Six ewes received saline at each time and acted as controls. Serial blood samples were collected at 10 or 15 min intervals between 0 and 8 h, 24 and 32 h, and 48 and 56 h after GnRH antagonist treatment and daily from oestrus (day 0) of the treatment cycle for 22 days. Oestrous behaviour was determined using a vasectomized ram present throughout the experiment. Progesterone secretion was episodic in both the early and late luteal phase with a frequency of between 1.6 and 3.2 pulses in 8 h. The GnRH antagonist abolished the pulsatile secretion and suppressed the basal concentrations of LH for at least 3 days after treatment. This suppression of LH, in either the early or late luteal phase, did not affect the episodic release of progesterone. Daily concentrations of progesterone in plasma showed a minimal reduction on days 11 to 14 after GnRH antagonist treatment on day 4, although this was significant (P < 0.05) only on days 11 and 13. There was no effect of treatment on day 11 on daily progesterone concentration, and the timing of luteolysis and the duration of corpus luteum function was unaffected by GnRH antagonist treatment on either day 4 or day 11. These results indicate that the episodic secretion of progesterone during the luteal phase of the oestrous cycle in ewes is independent of LH pulses and normal progesterone secretion by the corpus luteum can be maintained with minimal basal concentrations of LH.
已观察到，在母羊发情周期的黄体后期，孕酮分泌是间歇性的，且显然独立于促黄体生成素（LH）。本研究调查了在黄体早期或晚期抑制LH脉冲式释放对孕酮间歇性分泌的影响。在黄体期的第4天或第11天，对6只苏格兰黑脸母羊进行肌肉注射，剂量为1 mg/kg体重的强效促性腺激素释放激素（GnRH）拮抗剂。每次有6只母羊接受生理盐水注射并作为对照。在GnRH拮抗剂治疗后0至8小时、24至32小时以及48至56小时之间，每隔10或15分钟采集系列血样，并在治疗周期的发情期（第0天）开始每天采集血样，持续22天。在整个实验过程中，使用一只输精管结扎的公羊来确定发情行为。在黄体早期和晚期，孕酮分泌都是间歇性的，8小时内频率为1.6至3.2次脉冲。GnRH拮抗剂消除了脉冲式分泌，并在治疗后至少3天内抑制了LH的基础浓度。在黄体早期或晚期对LH的这种抑制，并未影响孕酮的间歇性释放。在第4天接受GnRH拮抗剂治疗后，血浆中孕酮的每日浓度在第11至14天显示出最小程度的降低，尽管仅在第11天和第13天具有显著性（P<0.05）。在第11天进行的治疗对每日孕酮浓度没有影响，黄体溶解的时间和黄体功能的持续时间不受第4天或第11天GnRH拮抗剂治疗的影响。这些结果表明，母羊发情周期黄体期孕酮的间歇性分泌独立于LH脉冲，并且黄体维持正常孕酮分泌所需的LH基础浓度极低。
