Abstract: Objective To identify if there was increased DNA damage in cardiomyocytes of rats with diabetic cardiomyopathy and also to evaluate the changes in gene expression of DNA repair enzymes 8-oxoguanine DNA glycosylase 1 (OGG1) and AP endonuclease 1 (APE1). Methods Total DNA，RNA and proteins of hearts were isolated in diabetes rat hearts. DNA damage was examined with quantitative polymerase chain reaction (Q-PCR) assay. mRNA and protein expressions of OGG1 and APE1 were detected with real time-polymerase chain reaction (RT–qPCR) and Western blot analysis. The levels of 8-hydroxy-2’-deoxy-guanosine (8-OHdG) in DNA were studied with ELISA. Results The damage of mtDNA was increased in rat hearts(P＜0.05) and there was not significant damage in nDNA. The amount of 8-OHdG in DNA was significantly increased(P＜0.05)，mRNA and protein expressions of OGG1 and APE1 were increased in diabetic rat hearts(P＜0.01). Conclusions The damage of mtDNA increased in diabetic rat hearts. Although the expression of OGG1 and APE1 increased in diabetic rat hearts，which can not repair the damage of the mtDNA. The increased mtDNA damage may contributes to myocardium damage.

Key words: DNA, DNA repair enzymes, Myocardium, Diabetic, Oxidative damage