THE EFFECT OF EMETINE ON METABOLISM AND CONTRACTILITY OF THE ISOLATED RAT HEART

¹ Council for Scientific and Industrial Research, Degenerative Diseases Group, Department of Medicine, University of Stellenbosch Medical School, Bellville, Republic of South Africa

The effect of emetine, a cardiotoxic agent, was studied on the metabolism and function of the isolated, perfused rat heart. Observations were made by means of a modified Langendorif perfusion system and a differential myographic force transducer. Substrates used were glucose-C¹⁴ (uniformly labeled); palmitate-1-C¹⁴ and pyruvate-1-C¹⁴ and -3-C¹⁴. Emetine (0.008 mg/ml) depressed myocardial metabolism of pyruvate and glucose but had no effect on palmitate uptake. Oxygen uptake as well as C¹⁴O₂ formation were significantly depressed, indicating that emetine had an inhibitory effect on Krebs cycle activity. Emetine depressed heart rate, tension time per minute and the maximum rate of rise of isometric tension, whereas time to peak systolic tension development increased. The reduction in oxygen uptake could be associated with either the reduction in contractility or the reduced heart rate. Tension time index was not affected, indicating that the difference in tension time per minute could be attributed to the chronotropic effect of emetine. Oxygen consumption did not increase when the heart rate was increased by pacing. The significance of these findings is discussed.