Induction of mutations in mouse fm3a cells by treatment with riboflavin plus visible light and its possible relation with formation of 8-hydroxyguanine (7,8-dihydro-8-oxoguanine) in dna

Photosensitized formation of 8-hydroxyguanine (oh⁸Gua; 7,8-dihydro-8-oxoguanine, oxo⁸Gua) in cellular DNA and its repair was examined in mouse FM3A cells. oh⁸Gua was generated 7-fold above the background level by 10 min irradiation with visible light in the presence of riboflavin (160 μM) and repaired to 60-70% of initial level after 2 h post-incubation. By this treatment, mutation frequency that was measured by counting ouabain-resistant colonies, was increased 7-fold above the background frequency. The accumulation of unrepaired oh⁸Gua in DNA generated by treatment with riboflavin plus visible light correlates to induction of mutations. Thus, oh⁸Gua will contribute to the mutation induced by visible light as well as spontaneous mutations.