大鼠卵巢促性腺激素释放激素(GnRH)受体及其特性

Ovarian GnRH Receptor of Rat and its Properties

采用乳过氧化物酶-葡萄糖氧化酶法放射性碘标记国产GnRH激动剂D-色~6-GnRH,用阴离子交换柱层析分离纯化,自身置换曲线计算出标记物比活性为700～1000μCi/μg。^(125)Ⅰ-D-色~6-GnRH与大鼠卵巢细胞膜有特异性结合,结合不受P物质、胰高糖素、生长素释放抑制素、促甲状腺素释放激素、血管紧张素Ⅱ等的竞争抑制。^(125)ⅠD-色~6-GnRH与肾皮质、骨骼肌、心肌等没有特异性结合,与大鼠胎盘有部分结合。大鼠卵巢GnRH受体与垂体GnRH受体的亲和常数基本相同,Ka2.43×10~9M^(-1);结合位点为垂体的20%左右,46.06fm/mg蛋白。本实验表明大鼠卵巢存在着特异性的GnRH受体,有助于阐明GnRH及其类似物的垂体外作用机理。

High potent and stable D-Trp^6-GnRH was iodinated by the lactoperoxidase-glucose-oxidase method and mono-iodo form purified by chromatography on QAE-Sephadex A 25.The specific activity of the ^(125)-D-Trp^6-GnRH was measured by selfdisplacement in the ra-dioreceptorassay ranged 700～1000 μci/μg.^(125)I-D-Trp^6-GnRH was shown to specifically bindto ovarian membrane preparations of rat.The ^(125)I-labeled analog binding to ovarian mem-brane was not inhibited by substanse P,glucagan,somatostatin,TRH,and angiotonin Ⅱ.The ^(125)I-labeled analog was not binding to the membrane preparations of renal cortex,skeletalmuscle,cardiac muscle.The ^(125)I-labeled analog was partly binding to membrane preparationof placenta. The ovarian GnRH receptors have a binding affinity similar to that of the anteriorpituitary GnRH receptors, K_a 2.43 10~9M^(-1). The GnRH-binding capacity of ovarian mem-brane preparation is 46.06 fm/mg protein and 20 percent of that of anterior pituitary. The test demonstrates that there are GnRH receptors in the ovary of rat.It is conduc-tive to explaining mechanism of extrapituitary effects of GnRH and its analogs.