Aim To investigate the effects of adiponectin on endoplasmic reticulum stress injury of the 3～4 days SD rat cardiomyocytes,which was induced by the intervention of H2O2.Methods Primary cardiomyocytes were obtained from neonatal rat and cultured by enzymatic digestion methods.The morphology of neonatal rat cardiomyocytes was studied by phase contramicroscope.Its molecular markers were observed by α-actin immunocytochemistry.Primary 3～4 days cells were used in experiment,and they were randomly divided into control group,H2O2 group(200 μmol/L H2O2,2 h),H2O2+10 mg/L APN group,H2O2+20 mg/L APN group,and H2O2+30 mg/L APN group.The change of morphology of cardiomyocytes was observed by electron microscope.The content of lactate dehydrogenase(LDH) was detected by chemistry chromatometry;the cardiomycocytes apoptosis was detected by agarose gel electrophoresislevels and Annexin V-FITC/PI flow cytometry.The expressions of GRP78 and caspase-12 were detected by Western Blotting and RT-PCR.Results Adiponectin pretreatment significantly decreased the apoptosis rate(43.6%±3.8% vs 70.7%±6.4%),and the release of LDH(686.7±61.1 U/L vs 1411.5±189.7 U/L,P<0.05).The expression of GRP78 and caspase-12 attenuated(mRNA: 0.56±0.03 vs 1.25±0.50;0.83±0.04 vs 1.32±0.15),(protein: 0.66±0.03 vs 0.92±0.50;0.64±0.03 vs 1.24±0.50).Conclusion Oxidative stress enhances the expressions of GRP78 and caspase-12,and makes endoplasmic reticulum stress to start.Adiponectin which can attenuate endoplasmic reticulum stress,have a protective effect on myocardial cells.