AIM:To explore the role of Bcl-2 and PCNA expression in the injury of rat myoblasts induced by hydrogen peroxide (H2O2).METHODS:Rat myoblasts at growth phase were divided into 4 groups based on basic fibroblast growth factor (bFGF) and H2O2 levels:normal control group, bFGF group, model group (H2O2 group) and treatment group (bFGF+H2O2 group).The expression of Bcl-2 and Bax was observed by immunohistochemistry and fluorescence methods.The protein levels of Bax, Bcl-2 and PCNA were determined by Western blot.RESULTS:Compared with model group, both immunofuorescence and fluorescence in treatment group showed enhanced Bcl-2 and low expression of Bax.Furthermore, the results of Western blot showed up-regulated PCNA and Bcl-2 protein and decreased Bax expression in treatment group.CONCLUSION:Oxidative stress results in the pathologic changes of myoblasts, and the up-regulation of Bcl-2 and PCNA may attenuate myoblast injury.