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EVALUATION OF THE MUTAGENIC ACTIVITY OF 3-NBA (3-NITROABENZANTHRONE) USING STRAINS OF SALMONELLA TYPHIMURIUM WITH DIFFERENT LEVELS OF THE ENZYMES NITROREDUCTASE AND ACETYLTRANSFERASE
Citation:
KUMMROW, F., C. M. RECH, S. H. WARREN, AND G. UMBUZEIRO. EVALUATION OF THE MUTAGENIC ACTIVITY OF 3-NBA (3-NITROABENZANTHRONE) USING STRAINS OF SALMONELLA TYPHIMURIUM WITH DIFFERENT LEVELS OF THE ENZYMES NITROREDUCTASE AND ACETYLTRANSFERASE. Presented at VII Brazilian Congress for Environmental Mutagenicity, Carcinogenicity, and Teratogenicity, Natal, BRAZIL, May 03 - 06, 2005.
Description:
The 3-NBA (3-nitro-7H- benz[d,e]antracen-7-one) is extremely potent in the Ames test an useful test for mutagenicity, being a possible inducer of tumors in animals and possible carcinogen for human beings. 3-NBA was previously identified in the exhausts of diesel, particulate matter of air and soil. It has direct mutagenic activity, for the parent strain Salmonella typhimurium TA98, is comparable to 1,8-dinitropyrene that is, according to the literature, a very powerful mutagen.. To study the influence of the activity of enzymes nitroreductase and acetyltransferase on the bioactivation of this compound in Salmonella typhimurium the strains used were TA98DNP6 (deficient for acetyltransferase), TA98NR (deficient for nitroreductase), TA98 (with moderate activity of both), YG1021 (with activity increased for nitroreductase), YG1024 (with increased activity for acetyltransferase) and YG1041 (with activity increased of both). The role of the S9 mixture was also evaluated on behavior of the mutagenic activity of this compound. The maximum tested dose, the same amount tested in the absence of S9, was 1ng per plate for all strains. In the absence of S9 mixture, the results for TA98 NR, TA98 DNP6, YG1021 and YG1024 were 700.000, 350.000, 1.800.000, 4.000.000 and 7.500.000 revertants/mg respectively. In the presence of S9, the results were negative for strains TA98NR and TA98DNP6 for the tested doses; for strains TA98 and YG1021 the results were approximately 10 times less than in the absence of S9; and for YG1024 approximately 4 times less. For strain YG1041, the results were similar in the absence and presence of an S9 mixture (approximately 50.000.000 revertants/mg). In the case of the YG1041, the high activity of enzymes acetyltransferase and nitroreductase seems to compensate for the resulting detoxification of the addition of S9 observed for the other strains. The results achieved with YG1021 and YG1024 suggest that the enzyme acetyltransferase is probably more important in the bioactivation of this compound than nitroreductase. Results in the absence of S9 mixture for TA98NR and TA98DNP6 suggest the possible involvement of other enzymatic pathways that are not those evaluated in this study, such as the activation of the nitro group in other parts of molecule. In order to better understand the enzymatic mechanisms involved in the bioactivation of the 3-NBA, other compounds could be tested in parallel like the benzanthrone (which is similar to the 3-NBA without the NO2 group) or the ABA (3-aminobenzanthrone), that is a biotransformation product of the 3-NBA.