Murphey C R, Clark J W, Giles W R, Rasmusson R L, Halter J A, Hicks K, Hoyt B
Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77251.
Math Biosci. 1991 Sep;106(1):39-84. doi: 10.1016/0025-5564(91)90039-l.
A number of fundamental properties of intercellular conduction in simulated cylindrical strands of cardiac tissue are examined. The paper is based on recent biophysical information describing the transmembrane ionic currents in bullfrog atrial cells as well as anatomical data on the structures (gap junctions) responsible for the coupling between cells in that tissue. A mathematical model of the single bullfrog atrial cell based on suction microelectrode single-cell voltage clamp data is employed, as well as a modified version of the well-known model of Heppner and Plonsey, to characterized the resistive connections between adjacent cells in a cardiac strand. In addition, the simulated cellular strand is assumed to be encased in a cylindrical, resistive endothelial sheath, thus forming an idealized atrial trabeculum; the trabeculum is immersed in an extensive volume conductor. It is possible to simulate both uniform and discontinuous conduction in this atrial strand model by appropriately changing the resistance of the intercalated discs that occur at cell boundaries. The conduction velocity achieved in the normal or control case is within the range of conduction velocities that have been measured for bullfrog atrial trabeculae using optical methods. Extracellular resistance is shown to have a significant effect on both conduction velocity and the critical value of disc resistance at which discontinuous conduction first occurs. Since the atrial cell model employed in this study is based on experimental data and can accurately simulate the atrial action potential, the transmembrane ionic currents generated by the model are capable of providing detailed information concerning the mechanisms of intercellular current spread, particularly in the region of the intercalated disc.
本文研究了模拟心脏组织圆柱状肌束中细胞间传导的一些基本特性。该论文基于近期描述牛蛙心房细胞跨膜离子电流的生物物理信息，以及关于该组织中细胞间耦合所涉及结构（缝隙连接）的解剖学数据。采用了基于吸液微电极单细胞电压钳数据的单个牛蛙心房细胞数学模型，以及Heppner和Plonsey著名模型的改进版本，来表征心脏肌束中相邻细胞之间的电阻连接。此外，假设模拟的细胞肌束包裹在圆柱形电阻性内皮鞘中，从而形成理想化的心房小梁；小梁沉浸在广阔的容积导体中。通过适当改变细胞边界处闰盘的电阻，可以在这个心房肌束模型中模拟均匀和不连续传导。正常或对照情况下实现的传导速度在使用光学方法测量牛蛙心房小梁的传导速度范围内。结果表明，细胞外电阻对传导速度和首次出现不连续传导时的闰盘电阻临界值都有显著影响。由于本研究中使用的心房细胞模型基于实验数据，并且能够准确模拟心房动作电位，因此该模型产生的跨膜离子电流能够提供有关细胞间电流传播机制的详细信息，特别是在闰盘区域。
