Simulations demonstrated that subcellular Na+ channel distribution, particularly in the lateral membrane, is critical for stable action potential propagation under reduced gap-junctional coupling.
Subcellular distribution of Na+ channels, particularly in the lateral membrane, plays a crucial role in maintaining stable cardiac action potential propagation when gap-junctional coupling is reduced.
The gap junction and voltage-gated Na(+) channel play an important role in the action potential propagation. The purpose of this study was to elucidate the roles of subcellular Na(+) channel distribution in action potential propagation. To achieve this, we constructed the myocardial strand model, which can calculate the current via intercellular cleft (electric-field mechanism) together with gap-junctional current (gap-junctional mechanism). We conducted simulations of action potential propagation in a myofiber model where cardiomyocytes were electrically coupled with gap junctions alone or with both the gap junctions and the electric field mechanism. Then we found that the action potential propagation was greatly affected by the subcellular distribution of Na(+) channels in the presence of the electric field mechanism. The presence of Na(+) channels in the lateral membrane was important to ensure the stability of propagation under conditions of reduced gap-junctional coupling. In the poorly coupled tissue with sufficient Na(+) channels in the lateral membrane, the slowing of action potential propagation resulted from the periodic and intermittent dysfunction of the electric field mechanism. The changes in the subcellular Na(+) channel distribution might be in part responsible for the homeostatic excitation propagation in the diseased heart.
Tsumoto et al. (Tue,) conducted a other in Cardiac conduction. Subcellular Na+ channel distribution vs. Gap junctions alone was evaluated on Action potential propagation. Simulations demonstrated that subcellular Na+ channel distribution, particularly in the lateral membrane, is critical for stable action potential propagation under reduced gap-junctional coupling.