Porter D A, Licht P
Gen Comp Endocrinol. 1985 Aug;59(2):308-15. doi: 10.1016/0016-6480(85)90383-1.
Dynamics of pituitary responsiveness to gonadotropin-releasing hormone (GnRH) as measured by LH and FSH secretion rates were examined for two species of ranid frogs in an in vitro superfusion system. The influence of sex was studied with juvenile bullfrogs, Rana catesbeiana, and responsiveness to long-term continuous superfusion with GnRH was examined in R. catesbeiana and R. pipiens. Female juvenile bullfrogs showed virtually no response to doses of GnRH up to 1000 ng/ml, whereas males responded to doses of GnRH as low as 10 ng/ml, and very large increments in LH and FSH were observed with 100 and 1000 ng/ml GnRH (responsiveness in the males was dependent on body size). Adult R. pipiens were more sensitive than bullfrogs to GnRH; 0.2 ng/ml GnRH was an effective dose. These data indicate that, relative to mammals, sensitivity to GnRH in frogs is higher than suggested by previous in vivo studies. As in mammals, "self-priming" in response to GnRH was evident; but unlike mammals, the "self-priming" occurred only after 7-12 hr of continuous superfusion with GnRH, and the R. pipiens glands were more resistant to desensitization during 48 hr of GnRH treatment. This study confirms that sex- and age-dependent differences in responsiveness to GnRH as well as "self-priming" found in previous in vivo studies are evidently dependent on properties of the anterior pituitary per se.
在体外灌流系统中，通过促黄体生成素（LH）和促卵泡激素（FSH）分泌率来检测两种蛙科蛙类垂体对促性腺激素释放激素（GnRH）反应的动态变化。利用幼年牛蛙（北美牛蛙，Rana catesbeiana）研究了性别的影响，并在北美牛蛙和豹蛙（R. pipiens）中检测了对GnRH长期持续灌流的反应。雌性幼年牛蛙对高达1000 ng/ml剂量的GnRH几乎无反应，而雄性牛蛙对低至10 ng/ml剂量的GnRH有反应，在100和1000 ng/ml GnRH作用下观察到LH和FSH有非常大的增加（雄性的反应性取决于体型大小）。成年豹蛙对GnRH比牛蛙更敏感；0.2 ng/ml GnRH是有效剂量。这些数据表明，相对于哺乳动物，蛙类对GnRH的敏感性高于先前体内研究显示的结果。与哺乳动物一样，对GnRH的“自身预激”很明显；但与哺乳动物不同的是，“自身预激”仅在连续用GnRH灌流7 - 12小时后出现，并且在GnRH处理48小时期间豹蛙的腺体对脱敏更具抗性。这项研究证实，先前体内研究中发现的对GnRH反应性的性别和年龄依赖性差异以及“自身预激”显然取决于垂体前叶本身的特性。
