Murphey C R, Clark J W, Giles W R
Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77251.
Math Biosci. 1991 Sep;106(1):85-109. doi: 10.1016/0025-5564(91)90040-p.
The success or failure of the propagation of electrical activity in cardiac tissue is dependent on both cellular membrane characteristics and intercellular coupling properties. This paper considers a linear arrangement of individual bullfrog atrial cells that are resistively coupled end to end to form a cylindrical strand. The strand, in turn, is encased by an endothelial sheath that provides a restricted extracellular space and an ion diffusion barrier to the outer bathing medium. This encased strand serves as an idealized model of an atrial trabeculum. Excitable membrane characteristics of the atrial cell are specified in terms of a Hodgkin-Huxley type of model that is quantitatively based on single-microelectrode voltage clamp data from bullfrog atrial myocytes. This membrane model can simulate the behavior of normal cells as well as of ischemic cells that exhibit depressed electrophysiological behavior (e.g., decreased resting potential, upstroke velocity, peak height, and action potential duration). Depressed activity can be easily simulated with variation of a single model parameter, the gain of the Na+/K+ pump current (INaK). Intercellular coupling properties are specified in terms of a lumped resistive T-type network between adjacent cells. The atrial strand model provides a means for studying the theoretical aspects of slow conduction in a "hybrid" strand that consists of a central region of cells having abnormal membrane or coupling properties, flanked on either side by normal atrial cells. Both uniform and discontinuous conduction are simulated by means of appropriate changes in the coupling resistance between cells. In addition, by varying either the degree of depressed electrical activity or the intercalated disc resistance in the central zone of the strand, slow conduction or complete conduction block in that region is demonstrated. Since the cellular model used in this study is based on experimental data and closely mimics both the atrial action potential and the underlying membrane currents, it has the potential to (1) accurately represent the current and voltage wave-forms occurring in the region of intercalated discs and (2) provide detailed information regarding the mechanisms in intercellular current spread in the region of slow conduction.
心脏组织中电活动传播的成功或失败取决于细胞膜特性和细胞间耦合特性。本文考虑单个牛蛙心房细胞的线性排列，这些细胞通过电阻方式首尾相连，形成一个圆柱形链。该链又被一层内皮鞘包裹，内皮鞘提供了一个受限的细胞外空间，并对外界浴液形成离子扩散屏障。这种被包裹的链作为心房小梁的理想化模型。心房细胞的可兴奋膜特性根据霍奇金 - 赫胥黎类型的模型来指定，该模型定量基于牛蛙心房肌细胞的单微电极电压钳数据。这个膜模型可以模拟正常细胞以及表现出电生理行为抑制（例如静息电位降低、上升速度、峰值高度和动作电位持续时间减少）的缺血细胞的行为。通过改变单个模型参数，即钠钾泵电流（INaK）的增益，可以轻松模拟抑制活动。细胞间耦合特性根据相邻细胞之间的集总电阻T型网络来指定。心房链模型提供了一种手段，用于研究由具有异常膜或耦合特性的细胞中心区域以及两侧正常心房细胞组成的“混合”链中慢传导的理论方面。通过适当改变细胞间的耦合电阻来模拟均匀和不连续传导。此外，通过改变链中心区域的电活动抑制程度或闰盘电阻，可以证明该区域的慢传导或完全传导阻滞。由于本研究中使用的细胞模型基于实验数据，并且紧密模拟了心房动作电位和潜在的膜电流，它有可能（1）准确表示闰盘区域中出现的电流和电压波形，以及（2）提供有关慢传导区域细胞间电流传播机制的详细信息。
