Recently, extremely high levels of endothelin-1 (ET-1) were detected in the pericardial fluid of patients undergoing open-heart surgery. ET-1 has been suggested to have direct arrhythmogenic effect on myocardium. The aim of the present study was to examine the putative arrhythmogenic effect of intrapericardial infusion of ET-1 in anesthetized dogs (n = 15). In preliminary experiments, ET-1 (0.125-1.0 nmol/min, n = 7) was infused into the closed pericardial sack for 40 min. ET-1 induced non-sustained and/or sustained ventricular tachyarrhythmias in all but the lowest dose. For detailed arrhythmia analysis in addition to standard ECG ventricular endocardial and epicardial monophasic action potentials (MAP) were recorded. ET-1 (0.250 nmol/min, n = 7) induced mono- and polymorphic ventricular tachycardias, which degenerated into ventricular fibrillation in two instances. Moderate if any ischemic signs could be detected before the onset of arrhythmias. The arrhythmias spontaneously disappeared in all instances with the exception when ventricular fibrillation terminated the experiment. QT interval (260 +/- 23 ms vs. 317 +/- 31 ms, P < 0.05), and endo- and epicardial MAPD90 (at 300 ms cycle length) prolonged significantly (in average 182 +/- 12 ms vs. 224 +/- 25 ms, P < 0.05). Using MAP recording afterdepolarizations were detected in three instances. In control animals (n = 3) arrhythmias were not observed and all electrophysiological parameters remained unchanged. The present results show that intrapericardial administration of ET-1 can induce ventricular arrhythmias in dogs. The arrhythmogenic effect of ET-1 may be based on prolongation of MAP duration and development of afterdepolarizations. However, the elucidation of the precise mechanism needs further investigation.