Abstract: ObjectiveTo explore the molecular mechanism of arsenic toxicology to cardiac muscle cell by detecting the expression of 8-nitro guanine,which was the biochemical marker of nuclear acid damage induced by reactive nitrogen species (RNS).MethodsDifferent concentrations of trioxide arsenic(As2O3)were administered to mice for consecutive 60 days, followed by decollation.Pathologic changes of cardiac muscle cell were detected by HE color ation.Immunohistochemistry method was used to investigate 8-nitrog uanine(8-NO₂-G)expression in cardiac muscle cell of mice.ResultsPathologic changes were observed in 1,2 and 4ppm groups.The expression of 8-NO₂-Gincreased significantly in experimental groups and was in a dose-effect relation(P<0.05).ConclusionThe low dose exposure of mice to arsenic RNSmay result in high expression of 8-NO₂-G.It indicated that the 8-NO₂-G may be the early bio-marker of cardiac muscle cell damage induced by arsenic.