Circulation Research an Official Journal of the American Heart Association Brief Reviews Intercellular Communication in Cardiac Muscle Intercellular Junction and the Electrical Coupling of Heart Cells
Circulation Research an Official Journal of the American Heart Association Brief Reviews Intercellular Communication in Cardiac Muscle Intercellular Junction and the Electrical Coupling of Heart Cells
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循环研究美国心脏协会官方杂志简要回顾心肌细胞间连接的细胞间通讯和心脏细胞的电耦合
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W. C. De Mello
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作者：
W. C. De Mello
多年来，心肌被概念为解剖学上的合胞体（Heidenhain, 1901; Godlewsky, 1902）。随着电子显微镜的发展，证明了心脏纤维是由被专门区域分隔的孤立细胞组成的，即所谓的嵌入盘（Sjostrand and Andersson, 1954）。椎间盘包括三个连接特化区：(1)黏着黄斑（桥粒），(2)黏着筋膜，和(3)间隙连接-在桥粒水平，相邻的质膜被250-300 a的间隙隔开，在相邻的细胞内可见纤维状物质，在其中心区域，可以看到几个结构以100 a的周期性桥接间隙（图1）。冷冻切割研究表明，这种联系的特征是紧密排列在六边形阵列中的颗粒，这些颗粒的直径通常为70-80 a，在中心区域显示点（20-25 a） （Gilula, 1978）。连接相邻细胞细胞质的亲水通道似乎穿过心肌的中心，由于心肌由具有高电阻表面膜的细胞组成，因此很难理解肌细胞的去极化如何在其邻近细胞中启动活动。人们考虑了化学机制的可能性（Sperelakis et al., 1960），乙酰胆碱酯酶在插层盘附近的定位（Joo and Czillik, 1962）明显支持了这一理论。然而，合成化学递质所需的复杂化学机制，以及突触囊泡，在心脏细胞中不存在。心脏细胞电耦合的概念是从不同类型的观察中出现的。当阈下脉冲注入心脏细胞时，浦肯野纤维中可以记录到电紧张电位，与细胞长度（125吉姆）相比，核心电阻率很低（105 8cm），空间常数更高（1.9 mm） （Weidmann, 1952），这表明细胞间连接具有低电阻（Weidmann, 1969）。在心肌纤维中，空间常数的值较小[1300 μ m] (Kamiyama和Matsuda， 1966)；880立方英尺（Weidmann, 1970）]，细胞内纵向电阻（470立方英尺/厘米）高于浦肯野纤维（Weidmann, 1970）。较高的Rj值可归因于肌原纤维和线粒体的密度，或较小的连接电导（Weidmann, 1970）。Barr et al.（1965）利用与Osterhout和Hill（1930）描述的方法相似的方法，表明沿…
THE heart muscle was conceptualized as an anatomical syncytium for many years (Heidenhain, 1901; Godlewsky, 1902). With the development of electron microscopy, it was proved that cardiac fibers are composed of isolated cells separated by specialized zones—the so-called intercalated discs (Sjostrand and Andersson, 1954). The discs comprise three junctional specializations: (1) the macula adhaerens (desmo-some), (2) the fascia adhaerens, and (3) the gap junc-At the level of desmosomes, the apposing plasma membranes are separated by a gap of 250-300 A and a fibrillar material is seen inside the adjacent cells, and in its central area, several structures are seen bridging the gap with a periodicity of 100 A (Fig. 1). Freeze-cleaving studies indicate that the nexus is characterized by particles closely packed in a hexagonal array These particles are usually 70-80 A in diameter showing dots (20-25 A) in the central region (Gilula, 1978). Hydrophilic channels connecting the cytoplasm of adjacent cells seem to pass through the center of the As cardiac muscle consists of cells with surface membrane of high electrical resistance, it became difficult to understand how the depolarization of a myocyte could initiate activity in its neighbors. The possibility of a chemical mechanism was considered (Sperelakis et al., 1960), and the localization of acetylcholinesterase near intercalated discs (Joo and Czillik, 1962) represented an apparent support for this theory. However, the complex chemical machinery required for the synthesis of a chemical transmitter, as well as synaptic vesicles, is absent in cardiac cells. The concept that the heart cells are electrically coupled has emerged from different types of observations. When a subthreshold pulse is injected into a cardiac cell, electrotonic potentials can be recorded in In Purkinje fibers, the core resistivity is quite low (105 8cm) and the space constant is higher (1.9 mm) in comparison with the length of the cells (125 jiim) (Weidmann, 1952), which indicates that the intercellular junctions have a low electrical resistance (Weidmann, 1969). In myocardial fibers, the values of space constants are smaller [1300 jum (Kamiyama and Matsuda, 1966); 880 jum (Weidmann, 1970)], and the intracellular longitudinal resistance (470 fl/cm) higher than in Purkinje fibers (Weidmann, 1970). This higher value of Rj can be ascribed to the density of myofibrils and mitochondria, or to a smaller junctional conduct-ance (Weidmann, 1970). Barr et al. (1965), utilizing a method similar to that described by Osterhout and Hill (1930), showed that the impulse conduction along a …