title: Photoactivation of mutagens.
abstract: Solutions of several promutagens or of non-genotoxic carcinogens were exposed to sunlight or to artificial sources of UV or fluorescent light, under various experimental conditions. Irradiation resulted in the oxygen-mediated formation of direct-acting mutagenic and DNA-damaging photoproducts in bacteria, with evident structure-activity relationship. Of the aromatic amines tested, 2-aminofluorene and, with lower efficiency, 2-acetylaminofluorene were photoactivated, whereas irradiation of 4-acetylaminofluorene and of the 1- and 2-amino substitutes of anthracene and naphthalene did not produce mutagenic derivatives in Salmonella typhimurium. Of the heterocyclic amines, 2-amino-3-methylimidazo[4,5-f]quinoline and 2-amino-3,4-dimethylimidazo[4,5-f]quinoline were extraordinarily sensitive to activation by sunlight and fluorescent light, which contrasted with the insensitivity of the tryptophan pyrolysis products. Use of optical and interference filters showed that near-UV light is the main component of solar radiation responsible for the formation of highly stable mutagenic derivatives. The mutagenicity of 2-aminofluorene and of the aminoimidazoquinoline compounds, following both metabolic and light activation, was lost in nitroreductase- and O-acetyltransferase-dificient bacteria. Benzo[alpha]pyrene was better activated by 254- than by 365-nm UV light. Sunlight did not affect the lack of mutagenicity of carcinogenic organochlorine pesticides, but exposure to 254-nm UV light selectively resulted in the formation of weak mutagens from dieldrin and 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene, but not from 4,4'-dichlorodiphenyltrichloroethane, lacking carbon-carbon double bonds.
authors.affiliation: Institute of Hygiene and Preventive Medicine, University of Genoa, Italy.
authors.forename: S
authors.initials: S
authors.lastname: De Flora
authors.forename: A
authors.initials: A
authors.lastname: Camoirano
authors.forename: A
authors.initials: A
authors.lastname: Izzotti
authors.forename: F
authors.initials: F
authors.lastname: D'Agostini
authors.forename: C
authors.initials: C
authors.lastname: Bennicelli
mesh_terms: D004260:DNA Repair / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics; D008027:Light; D009152:Mutagenicity Tests; D009153:Mutagens / Q000494:pharmacology / Q000528:radiation effects*; D012486:Salmonella typhimurium / Q000187:drug effects; D013472:Sunlight; D014466:Ultraviolet Rays
chemical_list: D009153:Mutagens