ALTERATIONS IN ELECTRICAL-ACTIVITY AND MEMBRANE CURRENTS INDUCED BY INTRACELLULAR OXYGEN-DERIVED FREE-RADICAL STRESS IN GUINEA-PIG VENTRICULAR MYOCYTES
ALTERATIONS IN ELECTRICAL-ACTIVITY AND MEMBRANE CURRENTS INDUCED BY INTRACELLULAR OXYGEN-DERIVED FREE-RADICAL STRESS IN GUINEA-PIG VENTRICULAR MYOCYTES
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DOI：
10.1161/01.res.72.6.1229
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发表时间：
1993-06-01
影响因子：
20.1
通讯作者：
COLE, WC
中科院分区：
文献类型：
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作者：
JABR, RI;COLE, WC
氧自由基(O-Rs)被认为可以引起心脏电活动的改变，然而，O-Rs对膜离子电流的影响及其对心脏离子通道的影响机制还没有很好的定义。在本研究中，我们研究了细胞内应用O-R产生系统后，豚鼠心室肌细胞静息膜电位和动作电位构型的时间依赖性变化以及稳态膜电流的变化。O-R由二羟基富马酸(3 MM)和FeCl3：ADP(0.05：0.5 mM)的组合加入到通过全细胞膜片钳技术记录膜电位和电流的移液管溶液中产生。细胞内暴露于O-R产生液可引起三个阶段的变化：1)早期去极化(5-10 mV)和动作电位时程增加伴随静息内向整流钾电流电导的降低；2)延迟后去极化和由Na+-Ca~(2+)交换介导的瞬时内向电流激活引起的触发活动，没有复极，并持续在-35-20 mV之间，反映了非选择性阳离子电流的刺激；3)晚期动作电位时程显著缩短，超极化和兴奋性丧失，并伴随着ATP敏感K+通道外向电流的激活。这些电活动和膜电流的变化可被羟基自由基清除剂N-(2-巯基丙酰基)甘氨酸(500微米)预处理所阻止。在细胞内钙离子螯合(吸管溶液中5 mM的EGTA)或用ryanodine(10微米)处理肌浆网钙时，与1和2期相关的改变完全消失，而与3期无关的改变完全消失。本研究表明，细胞内O-R应激引起膜离子电流的特异性改变，导致静息膜电位和动作电位构型的改变。此外，这些数据表明，由于肌浆网对钙的异常处理而导致的细胞内钙的升高是缺氧-再灌流过程中膜电流发生变化的原因之一。
Oxygen-derived free radicals (O-Rs) are thought to induce alterations in cardiac electrical activity; however, the underlying membrane ionic currents affected by O-Rs and the mechanisms by which O-Rs induce their effects on ion channels in the heart are not well defined. In this study, we investigated the time-dependent changes in resting membrane potential and action potential configuration and changes in steady-state membrane currents in guinea pig ventricular myocytes after intracellular application of an O-R-generating system. O-Rs were generated from the combination of dihydroxyfumaric acid (3 mM) and FeCl3: ADP (0.05:0.5 mM) added to the pipette solution that was used to record membrane potential and currents via the whole-cell variant of the patch-clamp technique. Intracellular exposure of myocytes to the O-R-generating solution induced three stages of changes: 1) an early depolarization (5-10 mV) and an increase in action potential duration accompanied by a decrease in resting inward rectifying K+ current conductance, 2) delayed afterdepolarizations and triggered activity caused by the activation of transient inward current mediated by Na+-Ca2+ exchange, with failure to repolarize and sustained depolarization between -35 and -20 mV, reflecting the stimulation of nonselective cation current, and 3) a late stage of marked decline in action potential duration, hyperpolarization, and loss of excitability accompanied by activation of the outward current through ATP-sensitive K+ channels. These alterations in electrical activity and membrane currents could be prevented by pretreatment with N-(2-mercaptopropionyl)glycine (500 muM), a scavenger of hydroxyl free radicals. The alterations associated with stages 1 and 2 but not stage 3 were completely abolished on intracellular Ca2+ chelation (5 mM EGTA in the pipette solution) or disruption of sarcoplasmic reticulum Ca2+ handling with ryanodine (10 muM). This study shows that intracellular O-R stress causes specific alterations in membrane ionic currents, leading to changes in resting membrane potential and action potential configuration. Moreover, the data indicate that an elevation in intracellular Ca2+ due to abnormal Ca2+ handling by the sarcoplasmic reticulum is a cause of some of the alterations in membrane currents during O-R stress.