Developmental changes in action potential prolongation by K +-channel blockers in chick myocardium

Abstract

The effects of K+-channel blockers on the action potential duration of the myocardium were examined in isolated right ventricles from the 7-10-day-old, 11-13-day-old, and 14-20-day-old embryo and 1-7-day-old hatched chicks. E-4031 significantly prolonged action potential duration at all developmental stages examined; the prolongation was largest in the 11-13-day-old embryo and was accompanied by early after-depolarizations. Chromanol 293B showed smaller prolongation at all stages examined. Terfenadine prolonged action potential duration in the 11-13-day-old embryo, but not in other stages. Thus, the chick ventricular myocardium changes its repolarization properties during development. © The Japanese Pharmacological Society.