Abstract: AIM:To study the protective effect of rhBNP postconditioning on acute myocardial ischemia/reperfusion injury in rabbits and its mechanism. METHODS: Thirty-six healthy rabbits were randomly divided into three groups with 12 rabbits in each group: sham-operated group, ischemia-reperfusion group and BNP postconditioning group. Blood vessels were not occluded in sham-operated group, a 40-min occlusion of the left coronary vessel was followed by a 180-min reperfusion of physiological saline in ischemia-reperfusion group and BNP was injected 5 min before and throughout the whole reperfusion in the BNP postconditioning group. Serum CK-MB was detected and recorded. Expressions of Bcl-2 and Bas were examined. RESULTS: Levels of CK-MB markedly increased in ischemia reperfusion group (P<0.01) compared with those in sham-operated group. The elevation of CK-MB obviously reduced in BNP postconditioning group. Myocardial cell apoptosis significantly reduced in BNP postconditioning group compared with that in I/R group. The expression of Bax increased and the expression of Bcl-2 decreased, which were contrary to those in BNP postconditioning group. CONCLUSION: Biochemical examinations show that BNP reduces myocardial infarction injury and increases the expression of Bcl-2, thus lowering myocardial apoptosis.