Blotner M, Shangold G A, Lee E Y, Murphy S N, Miller R J
Department of Pharmacological, University of Chicago Pritzker School of Medicine, IL 60637.
Mol Cell Endocrinol. 1990 Jul 9;71(3):205-16. doi: 10.1016/0303-7207(90)90026-5.
We have examined the pharmacology of the voltage-sensitive Ca2+ channels (VSCCs) that mediate gonadotropin secretion from primary cultures of rat pituitary cells, stimulated by either cell depolarization or by binding of gonadotropin-releasing hormone (GnRH). We also measured single-cell [Ca2+]i transients using fura-2 in gonadotropes identified by a reverse hemolytic plaque assay employing an antiserum to luteinizing hormone (LH). Cell depolarization evoked by either 50 mM K+ or 30 microM veratridine induced 2- to 6-fold increases in gonadotropin secretion over basal levels. GnRH caused 6- to 20-fold increases in follicle-stimulating hormone (FSH) and LH secretion, respectively, with maximal stimulation at 100 nM GnRH. K(+)- or GnRH-induced FSH release was largely prevented by co-incubation with 1 mM CdCl. Tetrodotoxin (TTX, 5 microM) prevented the veratridine-, but not the K(+)- or GnRH-induced, stimulation of FSH secretion. Nitrendipine (Ntd, 1 microM) produced 35-50% inhibition (NS) of both FSH and LH release stimulated by either 50 mM K+ or 100 nM GnRH. Ntd also inhibited the K(+)-induced [Ca2+]i rise (greater than 90%), as well as the secondary, plateau phase of the GnRH-induced elevation of [Ca2+]i (100% inhibition). Omega-conotoxin (omega-CgTx, 100 nM) partially suppressed FSH and LH release (NS) due to both K+ (33% each) and GnRH (44% and 18%, respectively). omega-CgTx showed variable effects on [Ca2+]i transients evoked by K+ or GnRH ranging from clear inhibition to no effect. We conclude that influx of extracellular Ca2+ is one of several fundamental events underlying the depolarization- or receptor-activated release of LH and FSH, and that this influx can be inhibited by dihydropyridine-sensitive ('L') Ca2+ channels. Two classes of L-channels may exist in gonadotropes, that differ in their sensitivity to omega-CgTx.
我们研究了电压敏感性钙通道（VSCCs）的药理学特性，该通道介导大鼠垂体细胞原代培养物中促性腺激素的分泌，可通过细胞去极化或促性腺激素释放激素（GnRH）结合来刺激。我们还使用fura - 2测量了通过反向溶血空斑试验鉴定的促性腺激素细胞中的单细胞[Ca2 +]i瞬变，该试验使用了抗黄体生成素（LH）的抗血清。50 mM K +或30 microM藜芦碱引起的细胞去极化导致促性腺激素分泌比基础水平增加2至6倍。GnRH分别使促卵泡激素（FSH）和LH分泌增加6至20倍，在100 nM GnRH时达到最大刺激。与1 mM CdCl共同孵育可大大阻止K（+）或GnRH诱导的FSH释放。河豚毒素（TTX，5 microM）可阻止藜芦碱诱导的，但不能阻止K（+）或GnRH诱导的FSH分泌刺激。尼群地平（Ntd，1 microM）对50 mM K +或100 nM GnRH刺激的FSH和LH释放产生35 - 50%的抑制（无统计学意义）。Ntd还抑制K（+）诱导的[Ca2 +]i升高（大于90%），以及GnRH诱导的[Ca2 +]i升高的次级平台期（100%抑制）。ω - 芋螺毒素（ω - CgTx，100 nM）部分抑制了由于K +（各33%）和GnRH（分别为44%和18%）引起的FSH和LH释放（无统计学意义）。ω - CgTx对K +或GnRH诱发的[Ca2 +]i瞬变显示出从明显抑制到无作用的可变影响。我们得出结论，细胞外Ca2 +的内流是LH和FSH去极化或受体激活释放的几个基本事件之一，并且这种内流可被二氢吡啶敏感的（“L”）Ca2 +通道抑制。促性腺激素细胞中可能存在两类L通道，它们对ω - CgTx的敏感性不同。
