Angiotensin II Type 1 Receptor Antagonist Protects Ventricular and Coronary Endothelial Function After 24-hour Heart Preservation

Abstract

Angiotensin II type 1 (AT1) receptor antagonists may enhance the cyclic guanosine monophosphate-nitric oxide system and thereby attenuate ventricular and coronary endothelial dysfunction after heart preservation. We used an isolated rabbit heart preparation perfused with blood from a support rabbit. The rabbit heart was excised, stored for 24 hours, and then perfused with blood from a support rabbit that was treated with an AT1 receptor antagonist (telmisartan; 5 mg/kg) or solvent. We evaluated the cardiac output with the working preparation, and coronary blood flow and coronary endothelial function with the Langendorff preparation. In addition, we measured the serum nitric oxide level in the coronary effluent. The Telmisartan Group showed higher plasma angiotensin II levels (928.6 +/- 136.2 vs 271.6 +/- 81.6 pg/ml, p < 0.01), better cardiac output (116.2 +/- 5.4 vs 88.8 +/- 7.1 ml/min, p < 0.05), and higher coronary blood flow (25.0 +/- 2.2 vs 14.9 +/- 1.3 ml/min, p < 0.01). The coronary blood flow in response to acetylcholine was higher in the Telmisartan Group (47.8 +/- 3.9 vs 28.0 +/- 2.1 ml/min, p < 0.01), but there was no difference in response to sodium nitroprusside. The Telmisartan Group showed higher serum nitric oxide levels in the coronary effluent (33.9 +/- 4.6 vs 20.6 +/- 3.3 mumol/liter, p < 0.05). Treatment with the AT1 receptor antagonist improved ventricular and endothelial function after 24-hour heart preservation. These data imply that AT1 activation plays a critical role in reperfusion injury. AT1 receptor blockade may be a promising strategy for long-term heart preservation.