Metabolic and genotoxic interactions of 2-aminofluorene and 2,4-diaminotoluene.
We have reported previously that the rodent carcinogen 2,4-diaminotoluene (2,4-DAT) is not activated as a mutagen to the standard Ames S. typhimurium tester strains when oxidized by prostaglandin H synthase (PHS). 2,4-DAT does, however, enhance the bacterial mutagenicity of the potent mutagen 2-aminofluorene (2-AF) when both compounds are incubated with the PHS activating system. Enhancement of activation of 2-AF would provide a plausible mechanism for the observed co-mutagenicity of 2,4-DAT. Co-incubation with 100 microM 2,4-DAT, however, inhibited the total metabolism of 25 microM 2-AF by 60% in both the PHS/H2O2 system and PHS/arachidonic acid system. The inhibition included a 75% decrease in the formation of water-soluble and protein-bound metabolites and about a 35% decrease in production of the peroxidative metabolites 2-nitrofluorene (NF) and 2-aminodifluorenylamine (ADFA). Azofluorene (AzF) production was the most sensitive to the effects of 2,4-DAT, exhibiting an 80% decrease in both PHS-catalyzed systems. No new 2-AF derived products were observed in the presence of 2,4-DAT. This pronounced inhibition of 2-AF metabolism by 2,4-DAT also was observed in incubations of the aromatic amines with PHS in the presence of S. typhimurium strain TA98. Bacterial N-acetylation of 2-AF did not appear to be an important reaction in any of these incubations. 2,4-DAT not only inhibited 2-AF metabolism by PHS, but also decreased the level of 2-AF covalent binding to the bacterial DNA by as much as 81%. This stands in sharp contrast to the enhancement of the mutagenicity of 2-AF elicited by 2,4-DAT in these same incubations. This clear dissociation between the extent of peroxidative activation, and resultant covalent modification of bacterial DNA, by 2-AF and the subsequent mutagenic response indicates that a metabolic interaction is not involved in the co-mutagenicity of 2,4-DAT.
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Department of Pharmacology, Toxicology and Therapeutics, University of Kansas Medical Center, Kansas City 66160-7417, USA.
Reed
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D000818:Animals; D016718:Arachidonic Acid / Q000737:chemistry / Q000378:metabolism; D002273:Carcinogens / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D004269:DNA, Bacterial / Q000187:drug effects; D005449:Fluorenes / Q000378:metabolism / Q000633:toxicity*; D008297:Male; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D010084:Oxidation-Reduction; D010655:Phenylenediamines / Q000633:toxicity*; D011451:Prostaglandin-Endoperoxide Synthases / Q000737:chemistry / Q000378:metabolism; D012486:Salmonella typhimurium / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D012756:Sheep
D002273:Carcinogens; D004269:DNA, Bacterial; D005449:Fluorenes; D009153:Mutagens; D010655:Phenylenediamines; D016718:Arachidonic Acid; C012177:2-aminofluorene; D011451:Prostaglandin-Endoperoxide Synthases; C010914:2,4-diaminotoluene