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细胞外pH值降低可增强豚鼠心室肌细胞持续性钠电流

马季骅, 罗岸涛, 王伟平, 张培华

武汉科技大学医学院心脏电生理研究室.湖北,武汉 430081

摘要

应用全细胞和单通道(贴附式)膜片钳技术观察胞外pH值降低对心室肌细胞持续性钠电流(persistent sodium current,Ⅰ_(Na.P))的影响,探讨其作用机制。结果显示:全细胞记录模式下,细胞外pH值降低可明显增大Ⅰ_(Na.P),且呈H~(+)浓度依赖性增强。当细胞外pH值从对照值的7.4降低为6.5时,Ⅰ_(Na.P)的电流密度从(0.347±0.067)pA/pF增加到(0.817±0.137)pA/pF({sl P}<0.01,{sl n}=6),而加入还原剂1,4--二硫甙苏糖醇(dithiothreitiol,DTT,1 mmol／L)后可使,Ⅰ_(Na.P)的电流密度回落到(0.233±0.078)pA／pF ({sl P}<0.01 vs pH 6.5,{sl n}=6)。单通道记录模式中,当细胞外pH值从对照值的7.4降低为6.5时,持续性钠通道的开放概率和开放时间分别从0.021±0.007和(0.899±0.074)ms增加到0.205±0.023和(1.593±0.158)ms({sl P}<0.01,{sl n}=6),再加入还原剂DTT(1 mmol／L)使开放概率和开放时间分别回落到0.019±0.005和(0.868±0.190)ms({sl P}<0.01 vs pH 6.5, {sl n}=6);加入蛋白激酶C(protein kinase C,PKC)抑制剂bisindolylmaleimide(BIM,5 #mu#mol/L)可使pH 6.5时增大的I_(Na.P)明显减小,开放概率和开放时间分别从0.214±0.024和(1.634±0.137)ms回落到0.025±0.006和(0.914±0.070)ms({sl P}<0.01 vs pH 6.5,{sl n}=6)。结果表明,细胞外pH值降低可诱发心室肌细胞I_(Na.P)增大,其机制可能与PKC的激活有关。

关键词： 持续性钠电流; pH值; 蛋白激酶C; 心室肌细胞

Low extracellular pH increases the persistent sodium current in guinea pig ventricular myocytes

Ma Jihua, Luo Antao, Wang Weiping, Zhang Peihua

Cardio-Electrophysiological Research Laboratory,Medical College,Wuhan University of Science and Technology.Wuhan 430081,Hubei

Abstract

Whole-cell and cell-attached patch-clamp techniques were used to record the changes of persistent sodium current (Ⅰ_(Na.P)) in ventricular myocytes of guinea pig to investigate the effect of low extracellular pH onⅠ_(Na.P) and its mechanism. The results showed that low extracellular pH (7.0, 6.8 and 6.5) obviously increased the amplitude of whole-cellⅠ_(Na.P) in a [H~(+)] concentration-dependent manner. Under the condition of extracellular pH 6.5,Ⅰ_(Na.P) was markedly augmented from control (pH 7.4) value of (0.347±0.067)pA/pF to (0.817±0.137) pA/pF (P<0.01, n=6), whereas the reducing agent dithiothreitiol (DTT, 1 mmol/L) could reverse the increased I_(Na.P) from (0.817±0.137) pA/pF to (0.233±0.078) pA/pF (P<0.01 vs pH 6.5, n=6). Reducing extracellular pH to 6.5 also increased the persistent sodium channel activity in cell-attached patches. The mean open probability and mean open time were increased from control value 0.021±0.007 and (0.899±0.074) ms to 0.205±0.023 and (1.593±0.158) ms, respectively (both P<0.01, n=6), and such enhancement could be reversed by application of 1 mmol/L DTT [to 0.019±0.005 and (0.868±0.190) ms, both P<0.01, n=6]. Furthermore, protein kinase C (PKC) inhibitor bisindolylmaleimide (BIM) 5 #mu#mol/L reduced the enhanced mean open probability and mean open time in pH 6.5 from 0.214±0.024 and (1.634±0.137) ms to 0.025±0.006 and (0.914±0.07) ms, respectively (both P<0.01, n=6). The results demonstrate that low extracellular pH can markedly increase the I_(Na.P) in guinea pig ventricular myocytes, in which activation of PKC may be invoveled.

Key words: persistent sodium current;pH;Protein kinase C;ventricular myocytes

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引用本文：

马季骅, 罗岸涛, 王伟平, 张培华. 细胞外pH值降低可增强豚鼠心室肌细胞持续性钠电流[J]. 生理学报 2007; 59 (2): 233-239.

Ma Jihua, Luo Antao, Wang Weiping, Zhang Peihua. Low extracellular pH increases the persistent sodium current in guinea pig ventricular myocytes. Acta Physiol Sin 2007; 59 (2): 233-239 (in Chinese with English abstract).