Objeclive To assess the effects of rhBNP on left ventrieular(LV)remodeling in rats with acute myocardial infaretion(AMI).Methods AMI was induced by ligating coronary arteryin male Sprague Dawley rats.Two days after surgery,AMI rats received intravenous infusion of rhBNP(15 μg/kg or 5 μg/kg once daily,n=15 each)or saline(placebo control,n=15)through Jugular Vein.Sham-operated mrs(a=15)served as normal control. Four weeks later,hemodynamie measurements were performed,left ventrieular weight (LVW),ratio of left ventfieular weight to body weight(LVW/BW),left ventrieular diameter(LVD)and infaret size were determined.P1asnla angiotensin Ⅱ and myocardial angiotensin Ⅱ levels were also measured.Results Compared with sham-operated rats,LVW,LVW/BW,LVD and myocardial angiotensin Ⅱ level were significantly increased,while the LV systolic pressure(LVSP),±dp/dt were significantly reduced in saline treated AMI rats(all P<0.05).LVW/BW,MI size,LVD and myocardial angiotensin Ⅱ in rhBNP treated AMI rats were significantly lower[LVW:(492.6±34.0)mg,(498.8±47.8)mg,(570.0±24.2)mg,P<0.01;LVW/BW:2.0±0.2,2.0±0.2,2.3±0.1,P<0.01;LVD:(25.3±2.9)%,(31.4±3.0)%,(46.4±3.0)%,P<0.01;myocardial angiotensin Ⅱ:(881.3±62.7)pg/L,(1186.0±94.5)pg/L,(2436.7±280.3)pg/L,P<0.05],while LVSP and ± dp/dt in rhBNP treatment groups were significantly increased than saline treated AMI rats f P<0.05 or P<0.01).Conclusion RhBNP is effective in attenuating left ventficular Itemodeling after AMI in rats.