Valenti S, Sarkissian A, Giusti M, Giordano G, Dahl K D
DISEM, University School of Medicine, Genova, Italy.
J Endocrinol Invest. 1997 Jul-Aug;20(7):381-6. doi: 10.1007/BF03347988.
The in vitro immunoreactive (i-LH) and bioactive (b-LH) LH release from hemipituitaries of intact adult male rats (INT) or rats castrated 7 days earlier (CAS) was studied. Hemipituitaries were incubated for 30 min (time 1) plus an additional 30 min (time 2) with GnRH (10 nM) and/or KCl (50 mM), according to one of the following protocols: media alone (C), KCl+KCl (K/K), GnRH+GnRH (G/G), KCl+GnRH (K/G), GnRH+KCl (G/K). All of the hemipituitaries were further incubated in media alone for 120 min (time 3). I-LH, b-LH and i-FSH were assayed on the media. In both models, the highest bioactive:immunoactive (b/i) ratio was noted during time 1; however, CAS always secreted more b-LH than INT at any given time of the study. In INT, GnRH--but not KCl--administration during time 2 resulted in blunted i-LH. During the same time, the b/i ratios decreased in all groups but G/K. LH secretion recovered during time 3 in all groups. In CAS, i-LH levels comparable to those of time 1 were sustained by either stimulus during time 2, while the b/i ratios were markedly decreased. LH secretion recovered in the K/K group during time 3. These results suggest that: 1) promptly releasable pools of b-LH are available in both models; 2) CAS always secrete more b-LH; 3) in INT, desensitization occurs involving parallel changes in both i-LH and b-LH, while changes in b-LH rather than i-LH are noted in CAS; 4) prolonged KCl administration might play a role in new gonadotropin synthesis and/or release.
研究了完整成年雄性大鼠（INT）或7天前阉割的大鼠（CAS）半垂体的体外免疫反应性促黄体生成素（i-LH）和生物活性促黄体生成素（b-LH）的释放情况。根据以下方案之一，将半垂体与促性腺激素释放激素（GnRH，10 nM）和/或氯化钾（KCl，50 mM）一起孵育30分钟（时间1），再额外孵育30分钟（时间2）：仅培养基（C）、KCl+KCl（K/K）、GnRH+GnRH（G/G）、KCl+GnRH（K/G）、GnRH+KCl（G/K）。所有半垂体再在仅含培养基的条件下进一步孵育120分钟（时间3）。对培养基中的i-LH、b-LH和i-FSH进行检测。在两种模型中，时间1时生物活性与免疫活性（b/i）的比值最高；然而，在研究的任何给定时间，CAS分泌的b-LH总是比INT多。在INT中，时间2给予GnRH（而非KCl）导致i-LH分泌减弱。在同一时间，除G/K组外，所有组中的b/i比值均下降。所有组在时间3时促黄体生成素分泌恢复。在CAS中，时间2的任何一种刺激均可使i-LH水平维持在与时间1相当的水平，而b/i比值则显著下降。K/K组在时间3时促黄体生成素分泌恢复。这些结果表明：1）两种模型中均存在可迅速释放的b-LH池；2）CAS总是分泌更多的b-LH；3）在INT中，脱敏反应涉及i-LH和b-LH的平行变化，而在CAS中则注意到b-LH而非i-LH的变化；4）长时间给予KCl可能在新的促性腺激素合成和/或释放中起作用。
