Mollard P, Kah O
CNRS URA 1200, Université de Bordeaux II, France.
Cell Calcium. 1996 Nov;20(5):415-24. doi: 10.1016/s0143-4160(96)90004-4.
The cytosolic free calcium concentration, [Ca2+]i, was monitored in single isolated goldfish gonadotrophs with the fluorescent probe Indo-1. It was found that goldfish gonadotrophs exhibit both spontaneous and secretagogue-induced [Ca2+]i rises. Spontaneous [Ca2+]i transients showed striking kinetic features and a sensitivity to external Ca2+ suggesting that they were the consequence of transient Ca2+ entries. Two kinetically distinct patterns of [Ca2+]i rises were generated in response to the two native forms of gonadotropin-releasing hormone (GnRH), salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II). In a part of the gonadotrophs, GnRHs triggered a plateau [Ca2+]i rise whereas in other responsive cells they induced a series of [Ca2+]i bursts, each consisting of grouped [Ca2+]i transients. Both plateau and burst [Ca2+]i response patterns were due to Ca2+ entry through plasma membrane Ca2+ channels, inasmuch as they were suppressed with external Ca2+ removal. No contribution of Ca2+ release from thapsigargin-sensitive stores was observed in either response pattern. While in mammalian gonadotrophs GnRH rises [Ca2+] by mostly acting on internal Ca2+ sequestering stores, our results show that GnRH-stimulated goldfish gonadotrophs rapidly increase Ca2+ entry to enhance their [Ca2+]i levels.
用荧光探针Indo-1监测单个分离的金鱼促性腺激素细胞中的胞质游离钙浓度[Ca2+]i。发现金鱼促性腺激素细胞表现出自发性和促分泌剂诱导的[Ca2+]i升高。自发性[Ca2+]i瞬变显示出显著的动力学特征以及对细胞外Ca2+的敏感性，表明它们是瞬时Ca2+内流的结果。针对两种天然形式的促性腺激素释放激素（GnRH），即鲑鱼GnRH（sGnRH）和鸡GnRH-II（cGnRH-II），产生了两种动力学上不同的[Ca2+]i升高模式。在一部分促性腺激素细胞中，GnRH引发[Ca2+]i平台期升高，而在其他反应性细胞中，它们诱导一系列[Ca2+]i爆发，每次爆发由成组的[Ca2+]i瞬变组成。平台期和爆发期[Ca2+]i反应模式均归因于通过质膜Ca2+通道的Ca2+内流，因为它们在去除细胞外Ca2+后受到抑制。在任何一种反应模式中均未观察到毒胡萝卜素敏感储存库释放Ca2+的作用。虽然在哺乳动物促性腺激素细胞中，GnRH主要通过作用于细胞内Ca2+螯合储存库来升高[Ca2+]，但我们的结果表明，GnRH刺激的金鱼促性腺激素细胞会迅速增加Ca2+内流以提高其[Ca2+]i水平。
