Figure 3.

Antioxidants inhibit UVA- and UVB-induced delayed mutagenesis. Cells were exposed to 321 kJ/m² UVA- (A) or 8.1 kJ/m² UVB radiation (B). The cells were grown with or without antioxidants in HAT-medium for 8 days after ultraviolet irradiation to kill early HPRT mutants. Subsequently, the cells were subcultured and grown with antioxidants in ordinary medium for 5 days before seeding in medium containing 5 μg/ml 6-thioguanine and no antioxidants. 0: medium without antioxidants, CAT: catalase, GSH: glutathione, SOD: superoxide dismutase. Error bars = standard error from 3–10 independent experiments each with 3–4 parallel dishes. *: significantly different from unirradiated cells (Mann-Whitney rank sum test, p < 0.05). Mutant frequency = number of mutant colonies per million cells seeded.