Aim To investigate the effect of different concentrations of adiponectin on ischemia-reperfusion myocardium and oxidative stress in rats,and their dose-effect relationship. Methods Eighty healthy Sprague-Dawley rats were randomly divided into five groups: sham-operated group,ischemia-reperfusion group(I/R),low,middle and high concentrations of adiponectin(60,120,180 ng/g) group,with 16 rats for each group.Sham group were suffered with sham operation.I/R group were undergone the left anterior descending branch of coronary artery ischemia for 45 min and reperfused for 180 min fusion.Rats in different adiponectin groups were infused with adiponectin for 30 min before ischemia-reperfusion.Then the rats in each group were then randomly divided into two sub-groups,eight rats in sub-group 1 and eight in sub-group 2.After reperfusion,the infarct size was determined by using Evans blue and TTC double dye staining in sub-group 1.In group 2 the left ventricular developed pressure(LVDP),±dp/dtmax were recorded at the end of reperfusion.At the end of experiment,the activities of total nitric oxide synthase(tNOS) and nitric oxide(NO)in the myocardium and superoxide dismutase(SOD) activity of serum were examined. Results Compared with sham-operated group,the level of tNOS and NO in the myocardium and serum SOD was downregulated in I/R group,whereas the cardiac infarct size was increased.The infarct size was reduced in different adiponectin groups compared with I/R group,while the levels of SOD,tNOS and NO were significantly increased with a dose-dependent improvement of ischemia/reperfusion-induced myocardial,contractile dysfunction was improved dose-dependently. Conclusion Adiponecin may protect hearts from ischemia-reperfusion injury in rats by reducing cardiac infarct size and improving myocardial contractile dysfunction.The molecular mechanism may involve preservation of tNOS,NO and SOD in serum and myocardial tissue,and protect myocardium from ischemia-reperfusion-induced oxidative stress.