Zhao Meimi, Feng Rui, Shao Dongxue, Liu Shuyuan, Lei Ming, Wang Hongmei, Sun Xuefei, Guo Feng, Hu Huiyuan, Kameyama Masaki, Hao Liying
Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China; Cardiovascular Institute of China Medical University, Shenyang 110001, China.
Department of Pharmaceutical Toxicology, School of Pharmacy, China Medical University, Shenyang 110122, China.
J Pharmacol Sci. 2015 Nov;129(3):143-9. doi: 10.1016/j.jphs.2015.08.001. Epub 2015 Aug 7.
This study aimed to investigate the intracellular Mg(2+) regulation of the L-type Ca(2+) channels in guinea pig ventricular myocytes. By adopting the inside-out configuration of the patch clamp technique, single channel currents of the L-type Ca(2+) channels were recorded at different intracellular Mg(2+) concentrations ([Mg(2+)]i). At free [Mg(2+)]i of 0, 10(-9), 10(-7), 10(-5), 10(-3), and 10(-1) M, 1.4 μM CaM + 3 mM ATP induced channel activities of 44%, 117%, 202%, 181%, 147%, and 20% of the control activity in cell-attached mode, respectively, showing a bell-shaped concentration-response relationship. Moreover, the intracellular Mg(2+) modulated the Ca(2+) channel gating properties, accounting for alterations in channel activities. These results imply that Mg(2+) has a dual effect on the L-type Ca(2+) channels: facilitation and inhibition. Lower [Mg(2+)]i maintains and enhances the basal activity of Ca(2+) channels, whereas higher [Mg(2+)]i inhibits channel activity. Taken together, our data from the application of an [Mg(2+)]i series suggest that the dual effect of Mg(2+) upon the L-type Ca(2+) channels exhibits long open-time dependence.
本研究旨在探讨豚鼠心室肌细胞中L型钙通道的细胞内镁离子（Mg²⁺）调节机制。采用膜片钳技术的内面向外式构型，在不同细胞内镁离子浓度（[Mg²⁺]i）下记录L型钙通道的单通道电流。在游离[Mg²⁺]i分别为0、10⁻⁹、10⁻⁷、10⁻⁵、10⁻³和10⁻¹ M时，1.4 μM钙调蛋白（CaM）+ 3 mM三磷酸腺苷（ATP）在细胞贴附模式下分别诱导出对照活性44%、117%、202%、181%、147%和20%的通道活性，呈现钟形浓度 - 反应关系。此外，细胞内Mg²⁺调节钙通道的门控特性，这解释了通道活性的改变。这些结果表明，Mg²⁺对L型钙通道具有双重作用：促进和抑制。较低的[Mg²⁺]i维持并增强钙通道的基础活性，而较高的[Mg²⁺]i则抑制通道活性。综上所述，我们应用一系列[Mg²⁺]i所获得的数据表明，Mg²⁺对L型钙通道的双重作用表现出长开放时间依赖性。
