The Arrhythmogenic Action of Endothelin in Rats

Endothelin (ET) was administered into the coronary ostia at doses of 0.1-1 microgram/kg in anesthetized rats. The ST segment was depressed at doses below 0.5 microgram/kg and was transiently elevated at 1 microgram/kg. Ventricular arrhythmias developed at doses above 0.5 microgram/kg. The arrhythmias that developed at 1 microgram/kg were precipitated into ventricular fibrillation. At the time when the arrhythmias developed, the ischemic changes had already subsided. These results suggest that ET may have an arrhythmogenic action, which is not solely attributable to myocardial ischemia.