MUTAGENICITY OF THE FULLERENE C-60-GENERATED SINGLET OXYGEN-DEPENDENTFORMATION OF LIPID PEROXIDES

Fullerene C-60 dissolved in polyvinylpyrrolidone was mutagenic for Sal monella strains TA102, TA104 and YG3003 in the presence of rat liver m icrosomes when it was irradiated by visible light. The mutagenicity wa s elevated in strain YG3003, a repair enzyme-deficient mutant of TA102 . The mutation was reduced in the presence of beta-carotene and parabr omophenacyl bromide, a scavenger and an inhibitor, respectively, of ph ospholipase, The results suggest that singlet oxygen was generated by irradiating the C-60 by visible light and that the mutagenicity was du e to oxidized phospholipids in rat liver microsomes. Of the phospholip ids in rat liver microsomes, the linoleate fraction isolated by high p erformance liquid chromatography was a major component, and played an important role in mutagenicity, Methyl linoleate, which was prepared f or gas chromatographic analysis, was readily oxidized to hydroperoxyme thyl linoleate, and associated with both 10- and 12-hydroxyl derivativ es with a double bond in chemical structure by singlet oxygen: radical s to the hydroxyl function were probably generated, Because of the ins tability of the hydroxymethyl linoleate radicals, guanine residues gen erated radicals, The results of ESR spectrum analysis suggested genera tion of radicals at the guanine base but not thymine, cytosine and ade nine bases as estimated with the g value of 2.0150, On the other hand, the singlet oxygen-generating C-60 formed 8-hydroxydeoxyguanosine (8- OH-dG) upon treatment with 2' deoxyguanosine and microsomes or linolea te, The formation of 8-OH-dG was highly elevated in the presence of mi crosomes and linoleate, The level of 8-OH-dG formed with and without t he microsome fraction was 47 and 9.6 units, respectively, per 10(4) de oxyguanosine, It was considered that the mechanism is indirect action of singlet oxygen due to lipid peroxidation of linoleate that causes o xidative DNA damage.