细胞外pH值降低可增强豚鼠心室肌细胞持续性钠电流  

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

作　　者：马季骅[1] 罗岸涛[1] 王伟平[1] 张培华[1] 

机构地区：[1]武汉科技大学医学院心脏电生理研究室,武汉430081

出　　处：《生理学报》2007年第2期233-239,共7页Acta Physiologica Sinica

基　　金：This work was supported by the Key Scientific Research Program of the Educational Bureau of Hubei Province (No. Z200511002).

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,ⅠNa.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ⅠNa.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,ⅠNa.P的电流密度从(0．347±0．067)pAJpF增加到(0．817±0．137)pA/pF(P< 0．01,n=6),而加入还原剂1,4-二硫甙苏糖醇(dithiothreitiol,DTT,1 mmol／L)后可使,ⅠNa.P的电流密度回落到(0．233±0．078)pA／pF (P<0．01 vs pH 6．5,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(P<0．叭,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(P<0．01 vs pH 6．5,n=6);加入蛋白激酶C(protein kinase C,PKC)抑制剂bisindolylmaleimide(BIM,5μmol/L)可使pH 6．5时增大的,ⅠNa.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(P<0．01 vs pH 6．5,n=6)。结果表明,细胞外pH值降低可诱发心室肌细胞ⅠNa.P增大,其机制可能与PKC的激活有关。Whole-cell and cell-attached patch-clamp techniques were used to record the changes of persistent sodium current （INaR） in ventricular myocytes of guinea pig to investigate the effect of low extracellular pH on/NaP and its mechanism. The results showed that low extracellular pH （7.0, 6.8 and 6.5） obviously increased the amplitude of whole-cell INaP in a [H^＋] concentration-dependent manner. Under the condition of extracellular pH 6.5,/Nap 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） reversed the increased INaP from （0.817±0.137） pA/pF to （0.233±0.078） pA/pF （P〈0.01 vs pH 6.5, n=6）. Decreasing extracelhilar 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 of 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 was reversed by application of 1 mmol/L DTT [to 0.019±0.005 and （0.868±0.190） ms, both P〈0.01 vs pH 6.5, n=6]. Furthermore, protein kinase C （PKC） inhibitor bisindolylmaleimide （BIM, 5μmol/L） reduced the enhanced mean open probability and mean open time at pH 6.5 from 0.214±0.024 and （1.634±0.137） ms to 0.025±0.006 and （0.914±0.070） ms, respectively （both P〈0.01 vs pH 6.5, n=6）. The results demonstrate that low extracellular pH markedly increases INaP in guinea pig ventricular myocytes, in which activation of PKC may be involved.

关 键 词：持续性钠电流 PH值 蛋白激酶C 心室肌细胞 

分 类 号：R331[医药卫生—人体生理学]