The detection and comparison of the genotoxic effects of some nitro aromatic compounds by the umu and SOS chromotest systems

Four nitroarenes were tested in two standard genotoxicity assay systems usi ng three well-known bacterial tester strains. The results were as follows: 4-nitroquinoline 1-oxide (4NQO) was positive in Quillardet and Hofnung's SO S chromotest using Escherichia coli strain PQ37 both in the presence and ab sence of microsomal (S9) supplements and in the Salmonella typhimurium umu tester strains NM2009 and NM3009, which express high levels of O-acetyltran sferase (O-AT) and O-AT plus nitroreductase (NR) respectively. m-Nitrocinna mic acid (m-NCA) was weakly positive in strains NM2009 and NM3009, but nega tive in the SOS chromotest; m-dinitrobenzene (m-DNB) was weakly positive in strain NM2009, intermediate positive in strain NM3009, but negative in the SOS chromotest; 2,4-dinitrotoluene (2,4-DNT) was weakly positive in strain NM3009, but negative in strain NM2009 and in the SOS chromotest. However i t still showed a dose-response relationship in strain NM2009. In view of th ese results, it is suggested that investigators planning to screen miscella neous nitroarenes for their genotoxicity in the future should consider taki ng advantage of the increased sensitivity which is conferred on S. typhimur ium strains NM2009 and NM3009 by virtue of their capacity to overexpress O- AT or O-AT and NR. (C) 1999 Elsevier Science Ireland Ltd. All rights reserv ed.