Bacterial mutagenicity, metabolism, and DNA adduct formation by binary mixtures of benzo[a]pyrene and 1‐nitropyrene

Air pollutants are a complex mixture containing polycyclic organic compounds. Among these are 1‐NP and B[a]P, which are important contributors to the mutagenicity of diesel exhaust and airborne particulate matters. To investigate the interaction of a complex mixture of airborne mutagens, the mutagenicity of 1‐NP was examined with S. typhimurium TA98 and TA98NR in the presence and absence of B[a]P. B[a]P exhibited a more antagonistic effect on the mutagenicity of 1‐NP in strain TA98 than in strain TA98NR. Also studied were (1) the inhibitory effects of B[a]P on the nitroreductive metabolism of 1‐NP and (2) DNA adduct formation by 1‐NP. Nitroreductase was associated with the metabolism of 1‐NP, and was reduced in a dose‐dependent manner in a binary mixture of 1‐NP and B[a]P. HPLC analysis showed that the amounts of 1‐AP and NAAP, the metabolites of 1‐NP, were significantly decreased by the addition of B[a]P in mixtures. The results indicate that the antagonistic effect of B[a]P on the mutagenicity of 1‐NP is mediated through altering its nitroreductive metabolism. © 1994 Wiley‐Liss, Inc.