A SUBPOPULATION OF CELLS WITH UNIQUE ELECTROPHYSIOLOGICAL PROPERTIES IN THE DEEP SUBEPICARDIUM OF THE CANINE VENTRICLE - THE M-CELL
A SUBPOPULATION OF CELLS WITH UNIQUE ELECTROPHYSIOLOGICAL PROPERTIES IN THE DEEP SUBEPICARDIUM OF THE CANINE VENTRICLE - THE M-CELL
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DOI：
10.1161/01.res.68.6.1729
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发表时间：
1991-06-01
影响因子：
20.1
通讯作者：
ANTZELEVITCH, C
中科院分区：
文献类型：
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作者：
SICOURI, S;ANTZELEVITCH, C
最近的研究表明，犬的心外膜和心内膜在电生理特性和药理反应方面存在差异，这种差异在很大程度上是由于心外膜存在显著的瞬时外向电流I(TO)和动作电位的尖峰和穹顶形态，而心内膜不存在。在试图量化这些差异并评估它们在整个室壁的分级时，我们遇到了心外膜下深层细胞的亚群，它们具有不同于心外膜或心内膜的电生理特征。这些细胞，我们称之为M细胞，表现出典型的心外膜的尖峰和穹顶的形态，但动作电位上移的最大上升速率明显大于心外膜或心内膜。以动作电位1相幅值的恢复作为I(TO)再激活的标志，我们发现M细胞具有显著的4-氨基吡啶敏感性I(TO)，其再激活时间过程由快和慢时间常数的两个分量组成。与心外膜或心内膜相比，M细胞动作电位时程的速率依赖性明显增强，与浦肯野纤维更为相似(组织学上未在该区域观察到)。在M细胞中从未观察到4相去极化，即使在儿茶酚胺和/或低[K+]o暴露后也是如此。综上所述，我们的研究提供了犬左、右室心外膜下深层存在一种独特的细胞亚群的证据，其电生理特征介于传导细胞和心肌细胞之间。虽然它们的功能尚不清楚，但M细胞可能促进心外膜传导，并可能影响或调节心电图J波、T波、U波和长QT间期的表现，并对心律失常的发生起重要作用。
Recent studies have shown that canine ventricular epicardium and endocardium differ with respect to electrophysiological characteristics and pharmacological responsiveness and that these differences are in large part due to the presence of a prominent transient outward current I(to) and a spike-and-dome morphology of the action potential in epicardium but not endocardium. In attempting to quantitate these differences and assess their gradation across the ventricular wall, we encountered a subpopulation of cells in the deep subepicardial layers with electrophysiological characteristics different from those of either epicardium or endocardium. These cells, which we have termed M cells, display a spike-and-dome morphology typical of epicardium but a maximal rate of rise of the action potential upstroke that is considerably greater than that of either epicardium or endocardium. Using the restitution of the amplitude of phase 1 of the action potential as a marker for the reactivation of I(to), we showed M cells to possess a prominent 4-aminopyridine-sensitive I(to) with a reactivation time course characterized by two components with fast and slow time constants. The rate dependence of action potential duration of M cells was considerably more accentuated than that of epicardium or endocardium and more akin to that of Purkinje fibers (not observed histologically in this region). Phase 4 depolarization was never observed in M cells, not even after exposure to catecholamines and/or low [K+]o. In summary, our study presents evidence for the existence of a unique subpopulation of cells in the deep subepicardium of the canine left and right ventricles with electrophysiological features intermediate between those of conducting and myocardial cells. Although their function is unknown, M cells may facilitate conduction in epicardium and are likely to influence or mediate the manifestation of electrocardiographic J waves, T waves, U waves, and long QT intervals and contribute importantly to arrhythmogenesis.