Preservation of cardiac function and energy reserve by the angiotensin-converting enzyme inhibitor quinapril during postmyocardial infarction remodeling in the rat.

PURPOSE: Angiotensin-converting enzyme (ACE) inhibitors show beneficial long-term hemodynamic effects in chronically infarcted hearts. The purpose of this study was to test whether prevention of the deterioration of mechanical function by ACE inhibitors is related to beneficial effects on high-energy phosphate metabolism that is deranged in heart failure. METHODS: Twelve-week old rats were randomly assigned to ligation of the left coronary artery [mycardial infarction (MI)] or sham operation (Sham) and to the ACE inhibitor quinapril (+Q) (6 mg/kg/day per gavage) or placebo treatment. Eight weeks later, cardiac function was measured in the isolated heart by a left ventricular balloon (pressure-volume curves), and energy metabolism of residual intact myocardium was analyzed in terms of total and isoenzyme creatine kinase activity (spectrophotometry), steady-state levels [adenosine triptosphate (ATP), phosphocreatine], and turnover rates (creatine kinase reaction velocity) of high-energy phosphates [31P nuclear magnetic resonance (NMR)] and total creatine content [high-performance liquid chromatography (HPLC)]. RESULTS: Quinapril prevented post-MI hypertrophy and partially prevented left ventricular contractile dysfunction [maximum left ventricular developed pressure 166+/-6, 83+/-16 (p < 0.05 MI vs. Sham), 139+/-13 mm Hg (p < 0.05 quinapril treated vs. untreated) in Sham, MI and MI+Q hearts]. Residual intact failing myocardium showed a 17% decrease of MM-CK and a 16% decrease of mito-CK activity. Total creatine was reduced by 23%, phosphocreatine by 26% and CK reaction velocity by 30%. Parallel to improved function, treatment with quinapril largely prevented the impairment of energy metabolism occuring post-MI. CONCLUSIONS: quinapril treatment results in an improvement of high-energy phosphate metabolism, of energy reserve via the creatine kinase reaction, and of contractile performance post-MI