Formation of DMA Adducts in Vitro and in Salmonella typhimurium upon Metabolic Reduction of the Environmental Mutagen 1-Nitropyrene1

The polycyclic nitroaromatic hydrocarbon 1-nitropyrene is an environmental pollutant, a potent bacterial mutagen, and a car cinogen. Xanthine oxidase, a mammalian nitroreductase, cata lyzed the in vitro metabolic activation of this compound to DNAbound adducts. Maximum adduct formation occurred at pH 5.5 to 6.0 and was increased by the addition of catatase to the incubation medium. DMA binding from 1-nitropyrene was inhib ited by hydrogen peroxide, L-ascorbate, and glutathione. Enzy matic hydrolysis of the modified DMA and subsequent analysis by high-pressure liquid chromatography indicated the presence of one major and two minor adducts. The major adduct was characterized by mass spectrometry and nuclear magnetic res onance spectroscopy as A/-(deoxyguanosin-8-yl)-1-aminopyrene. The minor adducts appear to be decomposition products of the major adduct. When Salmonella typhimurium TA1538 was incu bated with 1-nitropyrene, a strong correlation was found be tween the extent of DMA binding and the frequency of induced histidine reversions. Analysis of the bacterial DMA indicated one major adduct which had Chromatographie properties and pK«s identical to those of A/-(deoxyguanosin-8-yl)-1-aminopyrene. These data indicate that N-hydroxy-1-aminopyrene is probably the mutagenic and DMA-binding species formed during the met abolic reduction of 1-nitropyrene.