Irvine C H, Alexander S L
Veterinary Science Department, Lincoln College, Canterbury, New Zealand.
J Endocrinol. 1988 May;117(2):197-206. doi: 10.1677/joe.0.1170197.
Pituitary venous blood was collected by a painless nonsurgical cannulation method from five ambulatory stallions at 5-min intervals for 5-6 h during the breeding season. In four adult stallions, statistical analysis showed that pulses of gonadotrophin-releasing hormone (GnRH) and LH were coincident (P less than 0.01), as were pulses of FSH and LH (P less than 0.05). Furthermore, the patterns of changes in concentration of FSH and LH were highly correlated in each of the four stallions. However, seemingly ineffective pulses of GnRH were also observed, with 28% of GnRH pulses failing to induce a significant gonadotrophin pulse. In the four adult stallions the amplitude of pituitary venous gonadotrophin pulses varied markedly but no correlation with GnRH pulse amplitude was observed. Peak secretion of FSH, but not LH, during pulses was correlated with the length of the interpulse interval. Consequently, the ratio of FSH to LH during peaks was least (P less than 0.02) when the interpulse interval was 30 min or less. Thus, differential FSH and LH secretion was achieved within a constant steroid milieu. Two stallions had regular contact with oestrous mares, and in these horses the secretion of GnRH and gonadotrophins occurred almost continuously with rapid, rhythmic pulses superimposed upon a tonic background. Mean (+/- S.D.) interval between GnRH pulses was 31.4 +/- 9.8 min and 27.7 +/- 10.1 min. This secretory pattern was not observed in the two stallions which had infrequent contact with oestrous mares, although the small numbers precluded statistical testing of this apparent difference. No GnRH pulses were observed in one of these stallions, while in the other mean (+/- S.D.) GnRH pulse interval was 45.0 +/- 48.7 min, the large variance being partly due to rapid pulses during a period in which the stallion teased mares. The fifth stallion was pubertal, and GnRH and LH secretion occurred in 15 and 0% of samples respectively, while low levels of FSH secretion were observed in 37% of samples and jugular testosterone levels were immeasurably low. We conclude that there is a statistically significant synchrony between pulses of GnRH, LH and FSH in the pituitary venous blood of stallions. Furthermore, decreasing intervals between gonadotrophin pulses result in a significant reduction in secretion of FSH but not LH.
在繁殖季节，采用无痛非手术插管法，每隔5分钟从5匹门诊种马采集垂体静脉血，持续5 - 6小时。对4匹成年种马的统计分析表明，促性腺激素释放激素（GnRH）脉冲和促黄体生成素（LH）脉冲同步（P < 0.01），促卵泡生成素（FSH）脉冲和LH脉冲也同步（P < 0.05）。此外，4匹种马中每一匹的FSH和LH浓度变化模式高度相关。然而，也观察到了看似无效的GnRH脉冲，28%的GnRH脉冲未能诱导出明显的促性腺激素脉冲。在4匹成年种马中，垂体静脉促性腺激素脉冲的幅度差异显著，但未观察到与GnRH脉冲幅度的相关性。脉冲期间FSH（而非LH）的峰值分泌与脉冲间期的长度相关。因此，当脉冲间期为30分钟或更短时，峰值期间FSH与LH的比值最小（P < 0.02）。这样，在恒定的类固醇环境中实现了FSH和LH的差异分泌。2匹种马与发情母马有规律接触，在这些马中，GnRH和促性腺激素的分泌几乎持续发生，快速、有节律的脉冲叠加在持续性背景之上。GnRH脉冲之间的平均（±标准差）间隔为31.4 ± 9.8分钟和27.7 ± 10.1分钟。在另外2匹与发情母马接触较少的种马中未观察到这种分泌模式，尽管样本数量少使得无法对这种明显差异进行统计学检验。其中一匹种马未观察到GnRH脉冲，而另一匹种马的GnRH脉冲平均（±标准差）间隔为45.0 ± 48.7分钟，差异大部分是由于该种马在挑逗母马期间出现快速脉冲。第5匹种马处于青春期，分别在15%和0%的样本中检测到GnRH和LH分泌，而在37%的样本中观察到低水平的FSH分泌，颈静脉睾酮水平低至无法测量。我们得出结论，种马垂体静脉血中GnRH、LH和FSH脉冲之间存在统计学上显著的同步性。此外，促性腺激素脉冲间隔的缩短导致FSH分泌显著减少，但LH分泌未减少。
