Comparative effects of pretreatment with captopril and losartan on cardiovascular protection in a rat model of ischemia-reperfusion

ONJECTIVES We sought to assess the comparative effects of pretreatment with captopril and losartan on myocardial infarct size and arrhythmias:in a rat model of ischemia-reperfusion. BACKGROUND Angiotensin-converting enzyme (ACE) inhibitors and angiotensin I I receptor blockers (ARBs) inhibit the renin-angiotensin systemin different ways. However, the comparative effects of pretreatment with ACE inhibitors or ARBs on acute myocardial infarct size and arrhythmias are unknown. METHODS We randomly assigned 117 female Sprague-Dawley rats into three grou ps: group N was the normal control; group C was given 40 mg/kg body weight per day of captopril in drinking water; and group L was given 40 mg/kg per: day of losartan in drinking water. After 10 weeks of pretreatment, 25 rats in each group were subjected to 17 min of left anterior descending coronary artery occlusion and 2 h of reperfusion with hemodynamic and electrocardio graphic monitoring. Fourteen rats in each group had blood samples drawn and aortic rings removed to study vascular reactivity. RESULTS Mortality during ischemia and reperfusion was lower in combined gro ups L and C than in group N (4.2% vs. 19.2%, p = 0.042). Rats treated with losartan had significantly higher levels of angiotensin II in their plasma. Hemodynamic variables were not significantly different among the three gro ups. The thresholds of ventricular fibrillation (VF) before occlusion and a fter reperfusion were significantly higher in groups L and C than in group N (1.99 +/- 0.24 and 1.93 +/- 0.27 vs. 1.23 +/- 0.17 mA, p = 0.04; 2.13 +/- 0.25 and 1.78 +/- 0.22 vs. 0.95 +/- 0.11 mA, p = 0.001). The average episo des of ventricular tachycardia (VT) and VF per rat were significantly less in groups L and C than in group N (0.96 +/- 0.2 and 1.2 +/- 0.3 vs. 2.8 +/- 0.4 mA, p < 0.001). Myocardial infarct size was significantly smaller in g roups L and C than in group N (34 +/- 3% and 35 +/- 3% vs. 44 +/- 3%, p = 0 .031, 0.043). Endothelium-dependent vasorelaxation induced by a calcium ion ophore (A23187) was increased in both groups but was only statistically sig nificant in group C (p = 0.020). CONCLUSIONS Losartan and captopril have similar cardiovascular protective e ffects in a rat model of ischemia-reperfusion. They increased the threshold of VF, decreased mortality and decreased episodes of VT and VF, as well as decreased myocardial infarct size. (C) 2000 by the American College Of Car diology.