Effect of L-4-thioproline on arrhythmias caused by acute myocardial ischemia in rabbits

L-4-thioproline (T) iv prolonged the latent period of ventricular arrhythmias caused by acute coronary artery ligation (CAL) in unanesthetized rabbits. T 100 mg/kg iv 9 min before CAL prolonged the latent period of ventricular premature beats (VP) from 1.7+/-0.6 to 7.4+/-2.0 min, ventricular fibrillation (VF) from 6.1+/-1.9 to 12.8+/-3.8 min. T iv within 1 min after CAL prolonged the latent period of VP from 1.5+/-0.5 to 6.2+/-1.3 min VF from 5.4+/-1.8 to 10.3+/-3.9 min. By suction electrodes, changes in functional refractory period (FRP) in different ischemic zones were recorded in anesthetized rabbits. T 100 mg/kg iv before CAL prevented the prolongation of FRP in central zones of ischemia and the shortening of FRP in boundary ischemic zones. T 100 mg/kg iv after CAL prevented only the prolongation of FRP in central zones of ischemic hearts, but no effect on FRP in boundary ischemic zones. However, given iv both before and after CAL, T decreased the extent of dispersion of FRP in ischemic hearts. Our results suggest that it is the decreasing effect of T on the dispersion of FRP in ischemic hearts that plays an important role of T on arrhythmias caused by acute ischemia shown by its palliative effect on the dispersion of FRP in ischemic hearts.