ELECTRICAL UNCOUPLING AND IMPULSE PROPAGATION IN ISOLATED SHEEP PURKINJE-FIBERS
ELECTRICAL UNCOUPLING AND IMPULSE PROPAGATION IN ISOLATED SHEEP PURKINJE-FIBERS
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DOI：
10.1152/ajpheart.1989.257.1.h179
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发表时间：
1989-07-01
影响因子：
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通讯作者：
MICHAELS, DC
中科院分区：
文献类型：
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作者：
JALIFE, J;SICOURI, S;MICHAELS, DC
电耦合的改变可能在心律和传导障碍的发展中起主要作用。我们使用微电极和线性浦肯野纤维来分析细胞间耦合对动作电位传播的相对重要性，并研究传导速度(θ)之间关系的变化。以及由三种已知可改变缝隙连接电阻的试剂(庚醇、高渗溶液和哇巴因)诱导的上升速度(Vmax)。正庚醇灌流(1.5-3.0 mM)可逆地导致β-theta的显著下降。并最终在Vmax已被.apprx减少时阻止。38%。传导延迟与细胞内电阻(Ri)的增加密切相关，细胞内电阻(Ri)是肌浆和连接电阻的总和，假设为一维电缆模型。用0.1-0.5 mM哇巴因或高渗泰罗德溶液(添加600 mM蔗糖)代替庚醇灌流得到定性相似的结果。相比之下，当Vmax与Theta通过将KCl从4 mm改变到20 mm来研究它们之间的关系，Vmax的降低与θ的变化具有很好的相关性。KCl超输液对Ri无明显影响。最后，我们开发了一个动作电位沿90个电耦合心脏细胞的一维链传播的计算机模型。通过系统地改变模型中的电偶合度或最大钠电导，并通过研究这些变化对传播和Vmax的影响，我们获得了有力的证据来支持我们的实验结果的有效性。总体数据提供了关于电去耦合对异常脉冲传播的作用的可检验的预测。
Alterations in electrical coupling may have a major role in the development of cardiac rhythm and conduction disturbances. We have used microelectrodes and linear Purkinje fibers to analyze the relative importance of cell-to-cell coupling on action potential propagation and to study the changes in the relationship between conduction velocity (.theta.) and upstroke velocity (Vmax) induced by three agents (heptanol, hypertonic solution, and ouabain) known to alter gap junction resistance. Heptanol superfusion (1.5-3.0 mM) reversibly led to a major decrease in .theta. and ultimately to block at a time when Vmax had been reduced by .apprx. 38%. Conduction delay was closely correlated with an increase in intracellular resistance (Ri), calculated as the sum of myoplasmic and junctional resistances, assuming a one-dimensional cable model. Qualitatively similar results were obtained by superfusion with 0.1-0.5 mM ouabain or hypertonic Tyrode solution (up to 600 mM sucrose added) instead of heptanol. In contrast, when the Vmax vs. .theta. relationship was studied by changing the KCl from 4 to 20 mM, decreases in Vmax correlated well with changes in .theta.. No significant effects on Ri were observed during KCl superinfusion. Finally, we developed a computer model of action potential propagation along a one-dimensional strand of 90 electrically coupled heart cells. By changing systematically the degree of electrical coupling or the maximum sodium conductance in the model and by studying the effects of these changes on propagation and Vmax, we obtained strong evidence supporting the validity of our experimental results. The overall data provide testable predictions regarding the role of electrical uncoupling on abnormal impulse propagation.