Li G R, Feng J, Yue L, Carrier M
Department of Medicine, Montreal Heart Institute and University of Montreal, Montreal, Quebec, Canada H1T 1C8.
Am J Physiol. 1998 Aug;275(2):H369-77. doi: 10.1152/ajpheart.1998.275.2.H369.
Limited information is available about transmural heterogeneity in cardiac electrophysiology in man. The present study was designed to evaluate heterogeneity of cardiac action potential (AP), transient outward K+ current (Ito1) and inwardly rectifying K+ current (IK1) in human right ventricle. AP and membrane currents were recorded using whole cell current- and voltage-clamp techniques in myocytes isolated from subepicardial, midmyocardial, and subendocardial layers of the right ventricle of explanted failing human hearts. AP morphology differed among the regional cell types. AP duration (APD) at 0.5-2 Hz was longer in midmyocardial cells (M cells) than in subepicardial and subendocardial cells. At room temperature, observed Ito1, on step to +60 mV, was significantly greater in subepicardial (6.9 +/- 0.8 pA/pF) and M cells (6.0 +/- 1.1 pA/pF) than in subendocardial cells (2.2 +/- 0.7 pA/pF, P < 0.01). Slower recovery of Ito1 was observed in subendocardial cells. The half-inactivation voltage of Ito1 was more negative in subendocardial cells than in M and subepicardial cells. At 36 degrees C, the density of Ito1 increased, the time-dependent inactivation and reactivation accelerated, and the frequency-dependent reduction attenuated in all regional cell types. No significant difference was observed in IK1 density among the regional cell types. The results indicate that M cells in humans, as in canines, show the greatest APD and that a gradient of Ito1 density is present in the transmural ventricular wall. Therefore, the human right ventricle shows significant transmural heterogeneity in AP morphology and Ito1 properties.
关于人体心脏电生理学中的跨壁异质性，目前可用信息有限。本研究旨在评估人类右心室中心脏动作电位（AP）、瞬时外向钾电流（Ito1）和内向整流钾电流（IK1）的异质性。使用全细胞电流钳和电压钳技术，在取自移植的衰竭人类心脏右心室的心外膜下、心肌中层和心内膜下层分离的心肌细胞中记录AP和膜电流。区域细胞类型之间的AP形态有所不同。在0.5 - 2Hz时，心肌中层细胞（M细胞）的动作电位时程（APD）比心外膜下和心内膜下层细胞更长。在室温下，当阶跃到 +60mV时，观察到的心外膜下细胞（6.9 +/- 0.8 pA/pF）和M细胞（6.0 +/- 1.1 pA/pF）中的Ito1明显大于心内膜下层细胞（2.2 +/- 0.7 pA/pF，P < 0.01）。在心内膜下层细胞中观察到Ito1的恢复较慢。Ito1的半失活电压在心内膜下层细胞中比在M细胞和心外膜下细胞中更负。在36℃时，所有区域细胞类型中的Ito1密度增加，时间依赖性失活和再激活加速，频率依赖性降低减弱。区域细胞类型之间的IK1密度未观察到显著差异。结果表明，与犬类一样，人类的M细胞显示出最大的APD，并且跨壁心室壁中存在Ito1密度梯度。因此，人类右心室在AP形态和Ito1特性方面表现出显著的跨壁异质性。
