Cardiac responses to epinephrine and norepinephrine during prolonged cholesterol and high fat feeding in rabbits

Abstract

1. 1. It has been observed that rabbits maintained on a high fat-cholesterol diet for periods ranging up to thirty-eight weeks, show no significant anoxic electrocardiographic changes (STT alterations) as compared with normal rabbits. 2. 2. Following injections of epinephrine in doses ranging from 100 to 500 μg, marked ventricular arrhythmias and even fatal ventricular fibrillation ensue in both normal and high fat-fed animals, although no significant ST-T changes were detectable. 3. 3. Following the injection of norepinephrine in doses of 100 and 200 μg., tachycardias of various types ensued only in fat-fed animals, but with higher doses (500 and 1,000 μg.) similar changes occurred in both normal and fat-fed animals. 4. 4. Norepinephrine under these conditions induces rather characteristic anoxic ST-T changes, but no ventricular fibrillation. 5. 5. Perfused isolated atherosclerotic hearts show diminished contractility and reduced responses to epinephrine and norepinephrine. 6. 6. It is concluded, therefore, that norepinephrine is less injurious than epinephrine to both the normal and the atherosclerotic heart.