Reciprocal ST segment changes reproduced in burn-induced subepicardial injury model in bullfrog heart

In our previous studies, by simply inducing burn injuries on bullfrog hearts or partially exposing their surface to high-potassium (K⁺) solution, we could reproduce a ST segment elevation in the electrocardiogram (ECG), which is a characteristic finding in human ischemic heart disease. In the present study, using our burn-induced subepicardial injury model, we could additionally reproduce "reciprocal" ST segment changes for the first time in frog hearts, mimicking those observed in human acute myocardial infarction. Immunohistochemistry demonstrated markedly decreased Na⁺/K⁺-ATPase protein expression in the ventricular surface after the burn injury. The loss of this pump expression in injured cardiomyocytes was thought to be responsible for the creation of "currents of injury" and the subsequent ST segment changes observed in acute myocardial infarction.