It has been proposed that electrophysiological changes following coronary artery occlusion result from inhibition of the adenine nucleotide translocase and that these changes can be reduced by carnitine infusion or reproduced by infusion of K+-atractyloside. In the present study, we recorded bipolar electrograms during serial 3- to 5-min occlusions of the left anterior descending coronary artery in open-chest, anesthetized dogs. DL-Carnitine (100-200 mg/kg iv) prior to coronary artery occlusion did not significantly alter ischemia-induced electrogram changes. L-Carnitine (100 mg/min ia) distal to the site of occlusion during coronary artery occlusion partially reversed ischemia-induced electrogram changes, but these effects resembled those produced by intra-arterial infusion of NaCl. During normal perfusion, intra-arterial infusion of K+-atractyloside (750 mumol/10 min) or equimolar KCl produced similar reversible flattening of perfused zone electrograms. Sodium atractyloside (750 mumol/10 min ia) did not produce electrogram changes. We conclude that 1) carnitine does not attenuate ischemia-induced electrogram changes in this model and 2) K+-atractyloside-induced electrogram changes are primarily due to K+.