Mutagenicity of oxidative DNA damage in Chinese hamster V79 cells

We have investigated the mutagenicity of oxidative DNA damage induced inV79 Chinese hamster lung fibroblast, and measured 8- hydroxydeoxyguanosine(8OHdG) levels as an indicator of this damage. A hydroxyl radicalgenerator, N,N'-bis(2-hydroxyperoxy-2-methoxyethyl)-1,4,5,8-naphthalene-tetra -carboxylic-diimide (NP-III), induced 8OHdG inV79 upon irradiation with 366 nm ultraviolet light (UV) for 15 min. 8OHdGwas determined by HPLC with electrochemical detection after anaerobicsample processing. The 8OHdG level in the cells treated without NP-III was0.49 per 10(5) dG, whereas levels in the cells treated with 5, 10 or 20microM NP-III and UV irradiation were 1.84, 4.06 or 6.95 per 10(5) dG,respectively. The 8OHdG induced by 20 microM NP-III with UV irradiationdecreased rapidly, and the half-life of the induced 8OHdG was approximately6 h. NP-III with UV irradiation also induced DNA strand breaks in all cellsuniformly, as determined by single cell gel assay. Mutant frequencies atthe hypoxanthine-guanine phosphoribosyltransferase (hprt) locus in V79 weredetermined 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 ofthe cells treated with 5, 10 or 20 microM NP-III and UV irradiation were14.9, 20.6 or 24.7 respectively. Treatment with 20 microM NP-III and UVirradiation decreased the cell number, determined 3 days after thetreatment, to 20.8%. These findings indicate that acutely induced oxidativeDNA damage including mutagenic 8OHdG is only weakly mutagenic in V79.