Abstract: Objective To determine the effects of Sodium Nitroprusside (SNP), superoxide dismutase (SOD) and catalase (CAT) on the expression of catalytic subunit of the DNA-dependent protein kinase (DNA-PKcs) and Ku70/80 heterodimer in cardiomycyte H9C2, as well as their expression in the myocardial tissues of SD rats. Methods H9C2 cells were co-cultured with SNP at concentreation of 10, 20 and 40mmol/L for 6 hours, SD rats were injected with normal saline, SNP, SNP+SOD, SNP+CAT or SNP+SOD+CAT. Western blot and immunohistochemistry assay were used to estimate DNA-PKcs and Ku 70/80 protein expression respectively. Results The expression of DNA-PKcs and Ku70/80 were increased in H9C2 cells co-cultured with SNP when compared with control group, but they would be decreased when treated with SOD or/and CAT. The expression of DNA-Pkcs and Ku70/80 in myocardial tissues of experimental groups were higher than the control. Conclusion Radical scavengers may role as a protective effect for sodium nitroprusside related injury in cardiac myocytes.

Key words: sodium nitroprusside, radical scavengers, cardiomycyte, catalytic subunit of DNA-dependent protein kinase, Ku70/80 heterodimer