Effects of Different Does of Losartan in Hemodynamics after Acute Myocardial Infarction in Rats

Objectives To Compare the effects of different doses of Losartan in the hemodynamics after acute myocardial infarction (AMI) in the rats, and to evaluate the dose-effect relation, and to compare with Enalapril. Methods Sham-operated were selected randomly to serve as non-infarction controls. AMI were made by ligating left coronary artery in female Wistar rats. Forty-eight hours after the procedure, the 123 surviving rats wre randomly divided into five groups of AMI contract and high-, middle- and Low-dose losartan and Enalapril. Losartan and Enalapril were delivered by direct gastric gavage. After 3 weeks of medical therapy, hemodynamic studies were performed in each group, and the rat heart were then fixed , and pathologic analysis were performed. Complete experimental data obtained in 64 rats were analyzed, comprising of sham-operated group, AMI controls, high-dose losartan group, middle-dose Losartan group, low-dose Losartan group, Enalapril group. Results There were no obvious differences among the five AMI groups with MI sizes were around 44.5～46.8% ( all P 0.05). Compared with sham-operated rats, the left ventricular and diastolic pressure (LVEDP) in AMI group were all obviously increased (P0.05 ～ 0.001). While the maximun left ventricular pressure rising and dropping rates (±dp/dtmax ) were all obviously reduced in AMI group (allP0.001). Compared with the AMI group, LVEDP were significantly decreased in all four treatment groups (P0.05 ～ 0.001), and the LVEDP and -dp/dtmax were all more significant in high- and middle-dose than in low-dose losartan group (P0.05).Conclutions High, middle and low dose of losartan are all effective in hemodynamics after AMI in rats, the higher the more effective.