Na⁺/H⁺ exchange (NHE) mediates myocardial ischemic and reperfusion injury. We examined the effects of dietary administration of the potent and selective NHE1 inhibitor cariporide on acute responses to coronary artery ligation and reperfusion in the anesthetized rat. Male Sprague-Dawley rats received control rat chow or an identical diet containing 3 parts per million of cariporide for 1 wk before 225 min of occlusion of the left main coronary artery or 45 min of occlusion followed by 180 min of reperfusion. Hearts were excised and divided into left ventricle, right ventricle, and interventricular septum for analysis of NHE1 mRNA expression and apoptosis by staining with terminal deoxynucleotidyl transferase-mediated nick end labeling. Ischemia and reperfusion were associated with a threefold elevation in NHE1 mRNA expression in control animals that was significantly reduced in cariporide-fed rats. Cariporide reduced mortality from 26% of animals to 0%. The incidence of all arrhythmias was significantly reduced, including ventricular fibrillation (from 42 to 0%) and ventricular tachycardia (from 81 to 15%), as well as the number of ventricular premature beats (from 70 ± 12 to 17 ± 6). Cariporide moderately reduced apoptosis only in the reperfused left ventricle to values not significantly greater than those in sham-operated animals, and this was associated with a significantly higher ratio of Bcl-2 to Bax. This study suggests that NHE inhibition with dietary cariporide represents an effective management of acute postinfarction responses.

sodium-hydrogen exchange; HOE-642; infarction; arrhythmias; sodium-hydrogen exchanger subtype 1 messenger ribonucleic acid expression; apoptosis

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