Early pharmacologic intervention may prevent the deterioration in endothelial function after experimental myocardial infarction in rats: effects of ibopamine and captopril

Abstract

Background: Endothelial function is progressively disturbed after myocardial infarction (MI), which may be related to both neurohumoral activation and hemodynamic alterations. Consequently, it may be suggested that drugs that favorably affect these factors may also have a positive effect on endothelial function. Methods and Results: Rats underwent coronary ligation (n = 24) or remained unoperated (n = 21), and were randomized to captopril (25 mg/kg/d) or ibopamine (10 mg/kg/d) or remained untreated. Treatment was started following MI and lasted 8 weeks, after which rats were sacrificed for in vitro studies. Left ventricular end-systolic pressure was higher in rats treated with captopril (83 ± 6 mmHg) and ibopamine (80 ± 3 mmHg), as compared with untreated MI rats (48 ± 6 mmHg, P < .01 for both). Increased plasma norepinephrine levels in MI rats were reduced by captopril and ibopamine (both P < .05). Infarct size was smaller in rats treated with captopril (26.7 ± 3.6%, P < .05) and ibopamine (31.4 ± 4.3%, P = NS), as compared with untreated rats (41.7 ± 2.4%). Maximal endothelium-dependent relaxation (E max; % precontraction) and the concentration of methacholine causing 50% Emax, expressed as negative log(pIC 50) were significantly reduced in aortic rings from MI control subjects (pIC 50 = 6.15 ± 0.06 mol/L, E max = 32.0 ± 4.2%), as compared with normal control subjects (pIC 50 = 6.57 ± 0.07 mol/L, P < .001; E max = 50.0 ± 4.9%, P = .022). Captopril (pIC 50 = 6.30 ± 0.08 mol/L, E max = 45.1 ± 7.0%) and ibopamine (pIC 50 = 6.60 ± 0.08 mol/L, E max = 43.8 ± 5.2%) improved these parameters in MI rats. Conclusion: The results demonstrate preservation of endothelial function by early pharmacologic intervention after experimental MI in rats in the setting of concomitant reduction in infarct size.