Sanford L M, Robaire B
Department of Animal Science, Macdonald College, Ste. Anne de Bellevue, Qué., Canada.
Can J Physiol Pharmacol. 1990 Feb;68(2):150-6. doi: 10.1139/y90-024.
The effects of season and estradiol on the secretion of gonadotropic hormones in adult Dorset X Leicester X Suffolk rams were studied. Control groups of intact and castrate rams, and castrate rams given estradiol replacement (approximately 11.5 pg/mL) via polydimethylsiloxane capsules (sc) were assessed for 1 year, beginning in August. Mean concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH), and prolactin (PRL) were determined every 2 weeks for all three groups of rams and measurements of testosterone concentration and scrotal circumference were taken on the intact rams. Pulsatile LH release and the LH response to a 2-micrograms dose (iv) of gonadotropin-releasing hormone (GnRH) were assessed for all rams when the testes of intact rams were redeveloped (late October), regressed (early February, late April), and redeveloping (early August). Season directly affected LH-pulse amplitude, which increased only in the control castrate rams between February and April. In October, LH-pulse frequency was the same in both groups of castrate rams, while in April, frequency in the estradiol-treated castrate rams was suppressed to intact ram values. Pituitary responsiveness to exogenous GnRH did not change throughout the year in either of the castrate groups, but along with LH-pulse amplitude, it was increased in August in the intact rams. Although FSH secretion was 14-fold higher in the control castrate rams than in the intact rams, seasonal-directional changes in mean concentration were similar. FSH concentration in the estradiol-treated castrate rams was stable throughout the year. PRL secretion never differed between the control castrate and intact rams but was enhanced in the estradiol-treated castrate rams, particularly during long days.
研究了季节和雌二醇对成年多塞特×莱斯特×萨福克公羊促性腺激素分泌的影响。从8月开始，对完整和去势公羊的对照组以及通过聚二甲基硅氧烷胶囊（皮下）给予雌二醇替代物（约11.5 pg/mL）的去势公羊进行了为期1年的评估。每2周测定所有三组公羊的促黄体生成素（LH）、促卵泡生成素（FSH）和催乳素（PRL）的平均浓度，并对完整公羊测量睾酮浓度和阴囊周长。当完整公羊的睾丸重新发育（10月下旬）、退化（2月初、4月下旬）和再次发育（8月初）时，对所有公羊评估LH的脉冲式释放以及对2微克剂量（静脉注射）促性腺激素释放激素（GnRH）的LH反应。季节直接影响LH脉冲幅度，仅在2月至4月间，对照组去势公羊的LH脉冲幅度增加。10月，两组去势公羊的LH脉冲频率相同，而在4月，经雌二醇处理的去势公羊的频率被抑制至完整公羊的水平。在任何一组去势公羊中，垂体对外源GnRH的反应性全年都没有变化，但与LH脉冲幅度一样，完整公羊在8月时增加。尽管对照组去势公羊的FSH分泌比完整公羊高14倍，但平均浓度的季节性变化趋势相似。经雌二醇处理的去势公羊的FSH浓度全年稳定。对照组去势公羊和完整公羊的PRL分泌没有差异，但经雌二醇处理的去势公羊的PRL分泌增加，尤其是在长日照期间。
