Tan R C, Osaka T, Joyner R W
Todd Franklin Cardiac Research Laboratory, Department of Pediatrics, Emory University, Atlanta, Ga. 30323.
Circ Res. 1991 Oct;69(4):965-74. doi: 10.1161/01.res.69.4.965.
An ischemic myocardial region contains cells with a depolarized resting membrane potential. This depolarization leads to an intercellular current flow between the ischemic region and the surrounding normal myocardial cells, which has been termed an "injury current." We have devised an experimental model system in which an isolated rabbit ventricular cell is electrically coupled to a model depolarized cell to evaluate the effects of this injury current on the electrical properties of a normal ventricular cell. We found that the action potential duration of the isolated cell could be reversibly altered by varying the coupling resistance such that the action potential duration was shortened by high values of coupling resistance but could be considerably prolonged by lower resistance coupling. We did not observe automaticity in the isolated cell as a consequence of coupling to the depolarized model. The changes in action potential duration were accompanied by alterations in the frequency at which the isolated cell could respond to repetitive stimuli. In addition, the depolarization of the isolated cell produced by the electrical coupling led to a significant increase in the cellular excitability. This last effect may be of particular importance in understanding the mechanisms for origination of arrhythmias in the border zone of myocardial ischemia.
缺血性心肌区域包含静息膜电位去极化的细胞。这种去极化导致缺血区域与周围正常心肌细胞之间的细胞间电流流动，这被称为“损伤电流”。我们设计了一个实验模型系统，其中将分离的兔心室细胞与模型去极化细胞电耦合，以评估这种损伤电流对正常心室细胞电特性的影响。我们发现，通过改变耦合电阻，分离细胞的动作电位持续时间可以可逆地改变，使得动作电位持续时间在高耦合电阻值时缩短，但在低电阻耦合时可显著延长。由于与去极化模型耦合，我们在分离细胞中未观察到自动节律性。动作电位持续时间的变化伴随着分离细胞对重复刺激做出反应的频率的改变。此外，电耦合引起的分离细胞的去极化导致细胞兴奋性显著增加。最后这一效应在理解心肌缺血边缘区心律失常的发生机制方面可能特别重要。
