EFFECT OF IBOPAMINE ON VENTRICULAR REMODELING AFTER EXPERIMENTAL MYOCARDIAL-INFARCTION - A COMPARISON WITH CAPTOPRIL

Remodeling after myocardial infarction (MI) is influenced not only by hemodynamic but possibly by neurohumoral factors as well. Ibopamine is an orally active dopamine agonist (DA) with both hemodynamic and neur ohumoral properties in humans. The latter property prevails in rats. T o study the dose-dependent effect of ibopamine on myocardial remodelin g and compare it with the effect of captopril, we randomized rats with (n = 27) or without (n = 27) experimental MI to captopril (25 mg/ kg/ day), low-dose ibopamine (10 mg/kg/day), high-dose ibopamine (30 mg/kg /day), or no treatment. After 8-week treatment, hearts were isolated a nd left ventricular (LV) function, LV cavity volume, and infarct size (IS) were evaluated. Both ibopamine and captopril significantly reduce d plasma norepinephrine (NE) levels in rats with MI. was significantly reduced as compared with that of controls. IS was reduced in all thre e active treatment groups as compared with untreated rats. LV cavity v olume was significantly increased in untreated rats with MI as compare d with controls. This dilatation was attenuated by both ibopamine and captopril. Ibopamine, comparable to captopril, administered early afte r coronary ligation reduced IS and subsequent ventricular dilatation, resulting in preservation of cardiac function in this rat model. This observation suggests a major role for neurohumoral activation in the p rocess of remodeling.