心筋細胞膜の電気特性

概要

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There have been multiple ionic current systems which contribute to the electrogenesis of the heart. Their precise mechanisms and roles in the cardiac action potential are difficult to define, because of the complexity of their regulatory functions and, in part, due to inadequate voltage control of the preparations under the study. Recent advent of the isolation procedure of a single cardiac cell and of the application of the voltage clamp method as well as the patch clamp technique to the myocytes has made it possible to approach the fundamental problems as to the function of the single ionic channel. The action potential of the heart muscle is mainly formed by flows of the fast Na+ current, the slow inward current and the K+ currents. The amplitudes and time-courses of these currents are determined by electrochemical gradient of each ion across the cell membrane and conductance changes governed by membrane voltage and time. In addition to above factors, the status of cellular energy supply, hormone-receptor bindings and intracellular free ionic concentrations such as Ca2+ have now been recognized as important determinants of gating mechanisms of the channel. The currents activated by these factors may play an essential role for the electrical activity of the heart not only under the physiological condition, but also under the pathological conditions.
日本膜学会の論文