Role of activated oxygen species on the mutagenicity of benzo[a]pyrene

Different scavengers of active oxygen species (superoxide dismutase, catalase, mannitol and dimethylfuran) were tested in the Ames Salmonella assay to determine the role of the reactive oxygen species in the benzo[a]pyrene (B[a]P) mutagenesis process. Exogenously added superoxide dismutase or catalase at 10-100 micrograms ml-1 top agar, or 3-12 mM mannitol showed no effect on B[a]P mutagenicity in the presence of S9 mix. However, dimethylfuran (DMF), a singlet oxygen scavenger, inhibited in a dose-related manner the mutagenic response of B[a]P in the presence of the microsomal fraction. DMF at 3 and 6 mM inhibited the number of revertants by 69 and 93% for strain TA 100, and 76 and 78% for TA98, respectively. DMF at these levels was neither toxic nor mutagenic to the bacteria. The result indicates that singlet oxygen may play an important role in promoting B[a]P mutagenicity.