Aim To study the effects and mechanism of Guanxinkang capsules on myocardial injury induced by isoproterenol in rats.Methods 30 male Wistar rats were randomly divided into 3 groups:control group,acute myocardial ischemia group and Guanxinkang capsules group.Rats were given injections of ISO subcutaneously.Electrocardiography were performed,serum and myocardium creatine kinase(CK),creatine kinase MBmass(CK-MB),lactate dehydrogenase(LDH) and nitric oxide(NO) were detected,and the levels of NO and endothelins(ET) in myocardium were measured as well.Results The rising degree of ST-T obviously decreased in Guanxinkang capsules group,and the levels of serum CK,CK-MB and LDH decreased in Guanxinkang capsules group,compared with those of acute myocardial ischemia group(P