Preventive effects of AT_1 receptor blocker Losartan on left ventricular remodeling after acute myocardial infarction in rat

Objective To assess the effect of Losartan in preventing left ventricular remodeling (LVRM) after acute myocardial infarction (AMI) in the rat.Methods Forty-one surviving AMI female SD rats were randomized to AMI controls (n=19) or Losartan [3 mg/(kg·d)]group(n=22).Meanwhile,sham-operated(n=10) and normal rats (n=10) were randomly selected to serve as non-infarction controls.Losartan was delivered by direct gastric gavage.Four weeks after the therapy,hemodynamic measurement was performed in each group.Subsequently,the rat hearts were fixed and pathological analysis was performed on them.Exxclusive of the rats with MI sizes35% or45%,complete experimental data were obtained in 35 rats,which were comprised of AMI (n=11),Losartan (n=10), sham-operated (n=6) and normal groups (n=8).Results There were on significant differences in all indices between sham-operated and normal rats (all P 0 05).There was also no significant difference in MI size between AMI and Losartan groups (43.4% vs 42.9%, P 0.05).Compared with sham-operated rats,the left ventricular (LV) end diastolic pressure (LVEDP),volume (LVV),absolute and relative weight (LVAW and LVRW) in AMI controls were all significantly increased ( P 0.01～0.001);and the maximum LV pressure rising and dropping rates (±dp/dt) and their corrected values by LV systolic pressure (±dp/dt/LVSP) in AMI group were also significantly reduced ( P 0.05～0.001).Compared with AMI controls,LVEDP,LVV,LVAW and LVRW in Losartan group were all significantly reduced (LVEDP:10.5 mmHg vs 18.7 mmHg, P 0.01;LVV:0.62 ml vs 0.75 ml, P 0.05;LVAW:613.5 mg vs 679.9 mg, P 0.05;LVRW:1.97 mg/g vs 2.52 mg/g, P 0.05),and+dp/dt/LVSP was also significantly increased (44.8 vs 38.8, P 0.01).Conclusion Losartan can effectively prevent from LV remodeling and improve LV systolic function after AMI in the rat.