Mutagenicity of oxidative DNA damage in Chinese hamster V79 cells

We have investigated the mutagenicity of oxidative DNA damage induced in V79 Chinese hamster lung fibroblast, and measured 8-hydroxydeoxyguanosine (80HdG) levels as an indicator of this damage, A hydroxyl radical generator, N,N'-bis(2-hydroxyperoxy-2-methoxyethyl)-1,4, 5,8-naphthalene-tetra-carboxylic-diimide (NP-III), induced 80HdG in V79 upon irradiation with 366 nm ultraviolet light (UV) for 15 min, 80HdG was determined by HPLC with electrochemical detection after anaerobic sample processing. The 80HdG level in the cells treated without NP-III was 0.49 per 10(5) dG, whereas levels in the cells treated with 5, 10 or 20 mu M NP-III and UV irradiation were 1.84, 4.06 or 6.95 per 10(5) dG, respectively, The 80HdG induced by 20 mu M NP-III with UV irradiation decreased rapidly, and the half-life of the induced 80HdG was similar to 6 h, NP-III with UV irradiation also induced DNA strand breaks in all cells uniformly, as determined by single cell gel assay, Mutant frequencies at the hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in V79 were determined as the number of 6-thioguanine-resistant cells per 10(6) cells. Mutant frequency of the cells without NP-III was 8.0, and frequencies of the cells treated with 5, 10 or 20 mu M NP-III and UV irradiation were 14.9, 20.6 or 24.7 respectively, Treatment with 20 mu M NP-PII and UV irradiation decreased the cell number, determined 3 days after the treatment, to 20.8%, These findings indicate that acutely induced oxidative DNA damage including mutagenic 80HdG is only weakly mutagenic in V79.