Rispoli L A, Nett T M
Department of Biomedical Sciences, Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, CO 80523, USA.
Anim Reprod Sci. 2005 Aug;88(1-2):57-74. doi: 10.1016/j.anireprosci.2005.05.004.
Reproduction in mammals is controlled by interactions between the hypothalamus, anterior pituitary and gonads. Interaction of GnRH with its cognate receptor is essential to regulating reproduction. Characterization of the structure, distribution and expression of GnRH receptors (GnRH-R) has furthered our understanding of the physiological consequences of GnRH stimulation of pituitary gonadotropes. Based on the putative topology of the amino acid sequence of the GnRH-R and point mutation studies, key elements of the GnRH-R have been identified to play a role in ligand recognition and binding, G-protein activation and internalization. Normally, reproductive function is mediated by GnRH-R expressed only on the membranes of pituitary gonadotropes. The density of GnRH-R on gonadotropes determines their ability to respond to GnRH. This density is highest just prior to ovulation and likely is important for complete expression of the pre-ovulatory surge of LH. Therefore, knowledge regarding what regulates the density of GnRH-R is essential to understanding changes in pituitary sensitivity to GnRH and ultimately, to expression of the LH surge. Regulation of GnRH-R gene expression is influenced by a multitude of factors including gonadal steroid hormones, inhibin, activin and perhaps most importantly GnRH itself.
哺乳动物的生殖受下丘脑、垂体前叶和性腺之间相互作用的控制。促性腺激素释放激素（GnRH）与其同源受体的相互作用对于调节生殖至关重要。GnRH受体（GnRH-R）的结构、分布和表达特征进一步加深了我们对GnRH刺激垂体促性腺细胞的生理后果的理解。基于GnRH-R氨基酸序列的推定拓扑结构和点突变研究，已确定GnRH-R的关键元件在配体识别与结合、G蛋白激活和内化过程中发挥作用。正常情况下，生殖功能由仅表达于垂体促性腺细胞膜上的GnRH-R介导。促性腺细胞上GnRH-R的密度决定了它们对GnRH的反应能力。这种密度在排卵前最高，可能对促黄体生成素（LH）排卵前高峰的完全表达很重要。因此，了解调节GnRH-R密度的因素对于理解垂体对GnRH敏感性的变化以及最终LH高峰的表达至关重要。GnRH-R基因表达的调节受多种因素影响，包括性腺甾体激素、抑制素、激活素，也许最重要的是GnRH本身。
