Evans J J, Youssef A H, Abbas M M, Schwartz J
University Department of Obstetrics and Gynaecology, Christchurch School of Medicine, Christchurch, New Zealand.
J Endocrinol. 1999 Nov;163(2):345-51. doi: 10.1677/joe.0.1630345.
For full fertility in the female ovulation is necessary, which is dependent on the production of a surge of LH. An understanding of the processes which result in the high levels of LH requires delineation of the activities of individual component cells. In this study the responses of gonadotrophs to two signalling hypothalamic peptides, GnRH and oxytocin, were investigated. A cell immunoblot method was used to identify and distinguish between cells which secrete LH and those which contain LH but do not secrete the glycohormone. Rats were killed on the morning of pro-oestrus, the pituitary collected and the cells dispersed onto a protein-binding membrane for study. Cells were then incubated with GnRH and oxytocin, after which the membranes including the attached cells were stained by immunocytochemistry for LH. GnRH increased the total number of immunopositive cells which were present in a concentration-dependent manner. The most prominent change after 2 h incubation was in the number of secreting cells, whereas after 4 h there was also a marked increase in numbers of nonsecreting cells. Oxytocin also increased the total number of immunopositive cells in a concentration-responsive manner, however the profile of action of oxytocin was different from that observed for GnRH. Oxytocin had a relatively greater effect on numbers of immunopositive nonsecreting cells. Thus, the results reveal the potential for gonadotrophs to be flexibly and appropriately modulated by selected hypothalamic peptides. When cells were preincubated with oxytocin prior to GnRH there was not an additive increase in the numbers of immunopositive cells, suggesting that the two agonists act, in a nonidentical manner, on similar cells. The increase in the total number of immunopositive cells implies that there was a production of LH or post-translational processing, induced by exposure to GnRH or oxytocin. The results confirmed the heterogeneity of gonadotrophs and the existence of functionally distinguishable subpopulations, and revealed a difference between the effects of GnRH and oxytocin on expression and secretion of LH.
对于女性而言，排卵是实现完全生育能力所必需的，而排卵依赖于促黄体生成素（LH）高峰的产生。要理解导致LH高水平的过程，需要明确各个组成细胞的活动。在本研究中，对促性腺激素细胞对两种下丘脑信号肽——促性腺激素释放激素（GnRH）和催产素的反应进行了研究。采用细胞免疫印迹法来识别和区分分泌LH的细胞与含有LH但不分泌该糖蛋白激素的细胞。在动情前期的早晨处死大鼠，收集垂体并将细胞分散到蛋白质结合膜上进行研究。然后将细胞与GnRH和催产素一起孵育，之后用免疫细胞化学方法对包括附着细胞的膜进行LH染色。GnRH增加了免疫阳性细胞的总数，且呈浓度依赖性。孵育2小时后最显著的变化是分泌细胞的数量，而孵育4小时后非分泌细胞的数量也显著增加。催产素也以浓度反应性方式增加了免疫阳性细胞的总数，然而催产素的作用模式与GnRH不同。催产素对免疫阳性非分泌细胞的数量影响相对更大。因此，结果揭示了促性腺激素细胞有被特定下丘脑肽灵活且适当地调节的潜力。当细胞在GnRH之前先用催产素预孵育时，免疫阳性细胞的数量没有相加性增加，这表明这两种激动剂以不同的方式作用于相似的细胞。免疫阳性细胞总数的增加意味着暴露于GnRH或催产素会诱导LH的产生或翻译后加工。结果证实了促性腺激素细胞的异质性以及功能上可区分的亚群的存在，并揭示了GnRH和催产素对LH表达和分泌的影响之间的差异。
