细胞内高镁对豚鼠心室肌细胞L-型钙通道活性的影响

High intracellular Mg^(2+) affects the activities of L-type calcium channel in guineapig ventricular myocytes

本文旨在研究细胞内高镁对离体豚鼠心室肌细胞L-型钙通道的单通道门控特性的影响。急性酶消化法分离豚鼠心室肌细胞,应用膜片钳膜内向外单通道记录模式观察不同浓度细胞内镁([Mg2+]i)对心肌细胞L-型钙通道单通道电流的影响。结果显示,对照组([Mg2+]i 0.9 mmol/L)的心肌细胞L-型钙通道相对活性为(176.5±34.1)%,而高镁组([Mg2+]i 8.1 mmol/L)钙通道相对活性显著降低至(64.8±18.1)%(P<0.05)。另外,8.1 mmol/L[Mg2+]i使心肌细胞L-型钙通道的平均开放时间缩短至对照组的约25%(P<0.05),但对通道平均关闭时间无明显影响。以上结果提示,细胞内高镁主要通过缩短通道平均开放时间抑制豚鼠心室肌细胞L-型钙通道的活性。

This study is aimed to investigate the effects of high intracellular Mg2＋ on L-type calcium channel in guinea-pig ventricular myocytes. The cardiomyocytes were acutely isolated with enzyme digestion method. By adopting inside-out configuration of patch clamp technique, single channel currents of the L-type calcium channel were recorded under different intracellular Mg2＋ concentrations（[Mg2＋]i）. In control group, which was treated with 0.9 mmol/L Mg2＋, the relative activity of calcium channel was（176.5 ± 34.1）%（n = 7）. When [Mg2＋]i was increased from 0.9 to 8.1 mmol/L（high Mg2＋ group）, the relative activities of calcium channel decreased to（64.8 ± 18.1）%（n = 6, P 〈 0.05）. Moreover, under 8.1 mmol/L Mg2＋, the mean open time of calcium channel was shortened to about 25% of that under control condition（P 〈 0.05）, but the mean close time of calcium channel was not altered. These results suggest that high intracellular Mg2＋ may inhibit the activities of L-type calcium channel, which is mainly due to the shortening of the mean open time of single L-type calcium channel.