LIGHT-DEPENDENT ACTIVATION OF 7,12-DIMETHYLBENZ[A]ANTHRACENE TO A POTENT GENOTOXICANT

7,12-Dimethylbenz[a]anthracene (DMBA), which is widely used in mutagen esis and experimental carcinogenesis, is activated to a mutagen by whi te fluorescent light, A 40 min exposure to white fluorescent light of Salmonella typhimurium TA98 plates treated with DMBA, in the absence o f exogenous metabolism, resulted in an similar to 30-fold increase in the number of histidine revertants, This phenomenon also occurs, with lesser intensity, with other promutagens, such as benzo[a]pyrene or 2- acetylaminofluorene, and in other Salmonella tester strains. Moreover, white fluorescent light is able to activate DMBA to a toxicant for Ch inese hamster V79 cells in culture, resulting in very low cell surviva l, Under these conditions, white fluorescent light-activated DMBA was shown to cause chromosomal aberrations, but not gene mutations, as det ermined by resistance to thioguanine, This white fluorescent light-dep endent activation of DMBA seems to be related to the formation of reac tive species, as the addition of vitamin E results in a reduction in t he number of histidine revertants induced by white fluorescent light i n S. typhimurium TA98.