Metabolism of 1-nitropyrene and formation of DNA adducts in Salmonella typhimurium

1-Nitropyrene is slowly reduced by intact cells of Salmonellatyphimurium to yield 1-aminopyrene and N-acetyl-1-aminopyreneplus six unidentified minor products. When the bacteria areexposed to tritiated 1-nitropyrene, increasing amounts of radioactivitybecome bound to DNA as the nitropyrene is metabolized. Enzymatichydrolysis of the labelled DNA yields low molecular weight labelledcompounds which probably represent nucleoside adducts formedby the reaction of nitropyrene metabolites with DNA. Resultswith appropriate mutant strains indicate that bacterial nitroreductasesare involved in activating nitropyrene to a reactive intermediatethat binds to DNA and that nitropyrene adducts in DNA are subjectto excision repair.