Gregg D W, Nett T M
Department of Physiology, Colorado State University, Fort Collins 80523.
Biol Reprod. 1989 Feb;40(2):288-93. doi: 10.1095/biolreprod40.2.288.
Concentrations of pituitary receptors for gonadotropin-releasing hormone (GnRH) are affected by GnRH and gonadal steroids. To test the hypothesis that estradiol-17 beta (E2) directly affects the number of GnRH receptors in the pituitary, independent of GnRH secretion, ovariectomized ewes with hypothalamic-pituitary disconnections (HPD) were given 25 micrograms (i.m.) of E2 (HPD + E2, n = 5) or oil (HPD + OIL, n = 5). Ovariectomized control ewes, with intact hypothalamic-pituitary axes (INT), also received either E2 or oil (INT + E2, n = 6; INT + OIL, n = 6). Blood samples were taken hourly for analysis of serum concentrations of luteinizing hormone (LH) from 4 h prior to until 16 h after treatment. Pituitaries were collected 16 h after treatment for analysis of GnRH receptors. Treatment with E2 increased concentrations of LH in serum beginning 12.7 +/- 0.6 h after injection in INT ewes but not in HPD ewes. Compared to INT + OIL ewes, E2 treatment increased (p less than 0.001) the number of GnRH receptors by 2.5-fold in INT ewes and by 2.0-fold in HPD ewes. These results suggest that although GnRH is necessary for secretion of gonadotropins, E2 alone can directly increase the number of GnRH receptors in the pituitary.
促性腺激素释放激素（GnRH）的垂体受体浓度受GnRH和性腺类固醇的影响。为了验证17β-雌二醇（E2）直接影响垂体中GnRH受体数量这一假说，该假说独立于GnRH分泌，对下丘脑-垂体分离（HPD）的去卵巢母羊给予25微克（肌肉注射）E2（HPD + E2，n = 5）或油剂（HPD + OIL，n = 5）。下丘脑-垂体轴完整（INT）的去卵巢对照母羊也接受E2或油剂（INT + E2，n = 6；INT + OIL，n = 6）。从治疗前4小时到治疗后16小时，每小时采集血样分析血清促黄体生成素（LH）浓度。治疗后16小时采集垂体分析GnRH受体。E2治疗使INT母羊注射后12.7±0.6小时开始血清LH浓度升高，但HPD母羊未升高。与INT + OIL母羊相比，E2治疗使INT母羊GnRH受体数量增加2.5倍（p < 0.001），使HPD母羊增加2.0倍。这些结果表明，虽然GnRH对于促性腺激素的分泌是必需的，但单独的E2可直接增加垂体中GnRH受体的数量。
