[Effects of the early administration of losartan on ventricular remodeling in rabbits with experimental myocardial infarction].

This study was carried out to investigate the effects of early administration of losartan on ventricular remodelling (VR) in rabbits with experimental myocardial infarction (MI). New Zealand rabbits underwent left coronary artery ligation. Four groups were analyzed: sham (G1; n = 13), MI (G2; n = 13), sham + Los (G3; n = 13) and MI + Los (G4; n = 13). Los (12.5 mg/kg/d) was administered 3 hours post-MI during 35 days when the animals were sacrificed. The hearts were isolated and perfused using Langendorff's technique to determine systolic and diastolic pressure-volume (P/V) curves. Hearts were weighed, fixed in formaline, cut from apex to base, and stained with Masson's trichrome and pricrosirius red. The heart weight (HW)/body weight (BW) ratio was used as an index of hypertrophy. Infarct size (IS; %), septum (SeT, mm) and scar thickness (ST, mm) were measured using morphometric analysis. Results were expressed as mean +/- SEM. IS was G2 = 25.38 +/- 5.31; G4 = 21.85 +/- 4.13 (NS). HW/BW was 3.45 +/- 0.16; 3.23 +/- 0.25; 2.87 +/- 0.16; 3.23 +/- 0.18 in G1, G2, G3 and G4, respectively. Los shifted the diastolic P/V relationship to the right in sham and MI (p < 0.05 vs sham), and did not modify the systolic relationship. Scar collagen concentration was lower in G4 (p < 0.05 vs G2). SeT was lower in G3 and G4 (p < 0.05 vs G2). In conclusion, the early administration of Los unfavorably modified post-MI-VR, increasing ventricular dilation and reducing scar collagen concentration and thickness.