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AIM: To investigate the cardiac protective effects of ghrelin in rat with myocardial injury induced by isoproterenol(ISO). METHODS: Rats were subcutaneously injected ISO 40 mg.kg-1.d-1 with or without ghrelin 1 or 10nmol.kg-1.d-1 for 2 d. Hemodynamic parameters including mean arterial blood pressure and left ventricular pressure were measured at 12 h after the last injection with ISO and/or ghrelin. Plasma lactate dehydrogenase (LDH)activity, plasma and myocardial contents of malondialdehyde (MDA), and conjugated diene were measured. Plasma ghrelin and endothelin-1 levels were assayed using radioimmunoassay methods. Endothelin-1 and ghrelin mRNA were determined using RT-PCR. RESULTS: About 45 % (5/11) of rats after treatment with ISO alone died during experimental periods. However, no rats died after administration with ghrelin 10 nmol.kg-1.d-1 (0/11, P＜0.05).Ghrelin also obviously ameliorated the hemodynamic disturbance in rats induced by ISO. The plasma LDH activity,contents of myocardial and plasma MDA, and conjugated diene level in plasma in ISO+G10 nmol.kg-1.d-1 group were decreased by 28 %, 34 %, 73 %, and 38 % compared with those of ISO group (all P＜0.01) respectively. ISOinduced endothelin-1 mRNA over-expression was inhibited and endothelin-1 level in plasma were inhibited by ghrelin1 and 10 nmol.kg-1-d-1. The ghrelin levels in plasma and ghrelin mRNA in myocardium were increased in the rats after injection of ISO. The plasma ghrelin level was further increased after ghrelin administration. CONCLUSION:Ghrelin has a protective effect against ISO-induced myocardial injury.