FORMATION OF 8-HYDROXYGUANINE IN DNA DURING MITOMYCIN-C ACTIVATION

DNA damage caused indirectly via reactive oxygen species generated dur ing reductive activation of mitomycin C was evaluated. This oxidative DNA damage was measured by determining the formation of 8-hydroxyguani ne in DNA exposed to chemically or enzymatically activated mitomycin C . The level of 8-hydroxyguanine was measured indirectly by determining formamidopyrimidine-DNA glycosylase-sensitive sites induced in plasmi d DNA exposed to mitomycin C and directly by a P-32-postlabeling assay for the modified base. Activation of mitomycin C by sodium borohydrid e in air, by H-2/Pt, or xanthine oxidase in N-2 caused increases in th e level of 8-hydroxyguanine. The extent of the increase varied accordi ng to the incubation conditions with the greatest increase being obser ved in DNA exposed to mitomycin C activated under hypoxic conditions. These results support a possible indirect mechanism for DNA damage cau sed by mitomycin C that is mediated by reactive oxygen species.