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The aim of the present study was to investigate whether postconditioning with simvastatin attenuated myocardial ischemia reperfusion injury by inhibiting the expression of high mobility group box 1 (HMGB1) in rat myocardium following acute myocardial ischemia. In total, 30 male Sprague-Dawley rats were divided into sham operation (sham; n=10), acute myocardial infarction (AMI; n=10) and simvastatin (sim; n=10) groups. The AMI and sim groups were subjected to ischemia for 30 min, followed by reperfusion for 180 min. The rats in the sim group were administered 20 mg/kg simvastatin intravenously 5 min prior to reperfusion. Subsequently, the infarct size, serum cardiac troponin (c-TnI), tumor necrosis factor (TNF)-a and myocardial malondialdehyde (MDA) levels and superoxide dismutase (SOD) activity were measured. Western blot analysis was used to detect the protein expression of HMGB1. Postconditioning with simvastatin was shown to decrease the infarct size and HMGB1 expression levels in the myocardium following AMI (P<0.05). In addition, postconditioning with simvastatin not only decreased the serum levels of c-TnI and TNF-α (P<0.05), but also inhibited the increase in MDA levels and the reduction in SOD activity (P<0.05). Therefore, postconditioning with simvastatin was shown to attenuate myocardial injury. The underlying mechanism may be associated with the down-regulation of HMGB1 expression in the ischemic myocardium. [ABSTRACT FROM AUTHOR]