title: 6-Nitrobenzo[a]pyrene can be denitrated during mammalian metabolism.
abstract: Nitropolycyclic aromatic hydrocarbons (nitroarenes), including 6-nitrobenzo[a]pyrene (6-NBap), occur in our environment and are mutagenic in bacterial mutagenesis assays. The mutagenicity of 6-NBaP is enhanced when rat liver S9 is added. To investigate the cause of this increased activity, the metabolism of 6-NBaP was carried out with a total rat liver homogenate obtained from 3-methylcholanthrene- (MC-) induced rats, a 9000 X g supernatant enzyme, and with both unwashed and washed microsomes. Ring-hydroxylated 6-NBaP was detected. On the basis of retention times for known standards in a high-performance liquid chromatographic system, benzo[a]pyrene (BaP) and 6-acetoxy-BaP (6-OAcBaP) were isolated as products. BaP was further characterized via ultraviolet (UV) and mass spectra and 6-OAcBaP by UV, mass, and nuclear magnetic resonance (NMR) spectra. 6-HydroxyBaP (6-OHBaP) was also detected by UV and mass spectra. It is suggested that BaP is formed via a nitroanion radical of 6-NBaP and undergoes metabolism, while the 6-OHBaP is acetylated to form 6-OAcBaP. The acetyl donor remains to be identified.
mesh_terms: D000818:Animals; D001564:Benzo(a)pyrene / Q000378:metabolism; D001580:Benzopyrenes / Q000378:metabolism*; D002273:Carcinogens / Q000378:metabolism*; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism; D009153:Mutagens / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D001580:Benzopyrenes; D002273:Carcinogens; D009153:Mutagens; D001564:Benzo(a)pyrene; C034699:6-nitrobenzo(a)pyrene