CALCIUM-DEPENDENT INACTIVATION OF THE DIHYDROPYRIDINE-SENSITIVE CALCIUM CHANNELS IN GH3 CELLS
CALCIUM-DEPENDENT INACTIVATION OF THE DIHYDROPYRIDINE-SENSITIVE CALCIUM CHANNELS IN GH3 CELLS
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DOI：
10.1085/jgp.92.4.531
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发表时间：
1988-10-01
影响因子：
3.8
通讯作者：
ARMSTRONG, DL
中科院分区：
文献类型：
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作者：
KALMAN, D;OLAGUE, PH;ARMSTRONG, DL
应用膜片电极在无细胞膜膜片和透析细胞中研究了哺乳动物垂体肿瘤细胞（GH3）钙通道的失活。由保持电位为-40 mV的去极化引起的钙电流主要通过一类通道，这些通道先前被证明是由二氢吡啶和camp依赖性磷酸化调节的（Armstrong和Eckert， 1987）。当移液液中不含外源性钙缓冲液时，通过这些通道的宏观钙电流在半小时内失活。10毫秒到稳态水平比峰值小40-75%。失活也被测量为测试脉冲期间峰值电流的减少，紧跟着一个预脉冲。通过(a)将移液管溶液中的游离钙缓冲至< 10-8 M，可以大大减少或消除失活；(b)用钡代替细胞外钙；(c)将预脉冲电压从+ 10 mV提高到+ 60 mV；或(d)增加细胞内cAMP的浓度，要么“直接”使用二丁基cAMP，要么间接使用福斯克林或血管活性肠肽激活腺苷酸环化酶。因此，GH3细胞中二氢吡啶敏感钙通道的失活仅发生在膜去极化导致钙离子进入和细胞内积聚时。
The inactivation of calcium channels in mammalian pituitary tumor cells (GH3) was studied with patch electrodes under voltage clamp in cell-free membrane patches and in dialzyed cells. The calcium current elicited by depolarization from a holding potential of -40 mV passed predominantly through one class of channels previously shown to be modulated by dihydropyridines and cAMP-dependent phosphorylation (Armstrong and Eckert, 1987). When exogenous calcium buffers were omitted from the pipette solution, the macroscopic calcium current through those channels inactivated with a half time of .apprx. 10 ms to a steady state level 40-75% smaller than the peak. Inactivation was also measured as the reduction in peak current during a test pulse that closely followed a prepulse. Inactivation was largely reduced or eliminated by (a) buffering free calcium in the pipette solution to < 10-8 M; (b) replacing extracellular calcium with barium; (c) increasing the prepulse voltage from + 10 to + 60 mV; or (d) increasing the intracellular concentration of cAMP, either ''directly'' with dibutyryl-cAMP or indirectly by activating adenylate cyclase with forskolin or vasoactive intestinal peptide. Thus, inactivation of the dihydropyridine-sensitive calcium channels in GH3 cells only occurs when membrane depolarization leads to calcium ion entry and intracellular accumulation.