Increase in beating rate of cultured chick cardiac myocytes by ethanol andinhibition of the increase by antiarrhythmic drugs

Drinking alcohol sometimes causes cardiac arrhythmia, but the precise mecha nism remains unknown. To study the mechanism, we investigated the effects o f ethanol exposure on the beating rate of cultured chick cardiac myocytes. Primary cultures of cardiac myocytes were prepared from the ventricles of 1 4-day-old chick embryos and then treated with ethanol which, in the range o f 0.3 to 1.5 vol%, increased the beating rate in a dose-dependent manner. E thanol (0.6 vol%) caused an increase in the beating rate, but disopyramide (5 mu g/ml) and procainamide (10 mu g/ml), Na+ and K+ channel blockers, inh ibited the increase in the beating rate significantly. Neither lidocaine (5 mu g/ml) nor mexiletine (2 mu g/ml), Na+ channel blockers, nor calcium ant agonist verapamil (5 ng/ml) inhibited the increase. However, tetraethylammo nium chloride (ranging from 15 to 30 mmol/l), a K+ channel blocker, inhibit ed the increase. These findings indicate that ethanol increases the beating rate of cultured chick cardiac myocytes via the activation of the K+ chann el. This experimental model may be useful in studying the effect of ethanol on the K+ channel.