에타놀이 심근 수축성에 미치는 영향

Abstract

The effects of ethanol on the myocardial contractile force and action potential were studied in isolated rabbit papillary muscles. All experiments were performed in HCO-a-buffered Tyrode solution which was aerated with 3% CO,-97% 0, and kept pH 7.35 at 35°C. Action potentials were measured by conventional microelectrode technique. Glass microelectrodes were filled with 3M KCI and had a resistance of 20~30 megohms. Ethanol depressed the contractility of the rabbit papillary muscle at concentrations between 1 and 20gm/1 dose-dependently; Ethanol reduced peak developed tension by 5% at a concentration of Igm/l, 15~0 at 2gm/I, 30% at 4gm/I, 50% at 6gm/I, and 80% at 12gm/I, respectively. There was no effect on resting tension. A similar degree of depression was observed in the maximum rate of tension development CdP/dt). The effects were reversible in all cases. Shortening of the action potential duration, especially 50% repolarization time, with the reduction in contractility. was the most characteristic change in the electrical properties. The amplitude and duration of action potential were decreased in a dosedependent manner by ethanol. The resting membrane potential, however, was unaffected by ethanol. The action potential duration in the muscle hypopolarized by 18mM K-Tyrode was also shortened, but its height remained almost unchanged. The results of this experiment suggest that the depression of the contractility by ethanol can be attributed to the shortening of action potential duration, especially to inhibition of Ca·current.