Nitrogen dioxide induces DNA single-strand breaks in cultured Chinese hamster cells

Gaseous nitric oxide (NO) and nitrogen dioxide (NO2) were tested for their potential to induce DNA single-strand breaks (SSBs) in Chinese hamster cells (V79 cells). The alkaline elution assay was used for the detection of SSBs. V79 cells were exposed to NO and NO2 in N2 in varying concentrations (0-500 p.p.m.) and over varying periods (5-30 min). NO treatment did not result in any detectable DNA damage. NO2 led to a dose- and time-dependent increase of the rate of SSBs and the amount was dependent on concentration of NO2 and the length of exposure. The lowest observable effective concentration which was statistically different from control values was 10 p.p.m. exposed for 20 min. The metabolites of both gases, nitrite (NO2-) and nitrate (NO3-), had no DNA-damaging activity up to a concentration of 1 mM. The mechanism by which NO2 may generate SSBs is discussed.