Abstract: ObjectiveTo explore the effects of sodium nitrite(NaNO₂)on cell proliferation and DNA damage in L929 fibroblasts.MethodsMethyl thiazol tetrazolium(MTT)method was used to evaluate the cellular toxicity of NaNO₂ on cell viability of L929 cells,and the single cell gel electrophoresis(SCGE)as well as KCl-sodium dodecyl sulfate(SDS) assay were implied to detect DNA damage and DNA-protein crosslink(DPC).ResultsHormesis was observed when L929 cells were exposed to certain concentrations of NaNO₂ for 48 hr with a hormetic zone from 0 to 0.0384 mg/L.Under the exposure of 0.02 mg/L and 1 500 mg/L NaNO₂,the tail length of DNA(2.72±1.99,3.26±3.09μm),tail DNA% (7.87±6.63,7.75±4.90%),and Olive tail moment(0.80±0.64,0.79±0.64)of L929 cells were significantly different from those of the control group(P<0.05).DPC was observed for the cells under exposures of 2 mg/L,20 mg/L,and 1 500 mg/L NaNO₂ compared with those of the control group in a dose dependent manner.ConclusionNaNO₂ can induce hormesis and DNA fracture damage in L929 cells.