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 microM0 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.