Metabolic activation of N-acetylbenzidine and N, N′-diacetylbenzidine to mutagens, using isolated hepatocytes and the 9000 × g liver supernatant from rat, hamster and guinea pig

doi:10.1016/0027-5107(85)90071-5

Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis

Volume 151, Issue 2, September 1985, Pages 195-200

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Abstract

The metabolic activation of MABZ and DABZ, forming products mutagenic towards Salmonella typhimurium TA1538, was studied with isolated hepatocytes from rat, hamster and guinea pig and the S9 fraction (9000 × g supernatant) prepared from these hepatocytes. Special attention was given to the influence of acetyl-CoA, the cofactor for N-acetylation, on the mutagenicity of these arylamides.

The rat and guinea pig S9 preparation activated MABZ as well as DABZ to a much higher degree than the intact hepatocytes of these animal species. Addition of acetyl-CoA to the S9 preparation decreased the mutagenicity of MABZ and DABZ.

On the contrary, for the hamster the mutagenicity of MABZ and DABZ appeared to be lower with the S9 preparation than with intact hepatocytes. Addition of acetyl-CoA to the S9 here increased the mutagenic activity of these arylamides.

In the presence of intact hepatocytes obvious interspecies differences were observed in the activation of MABZ and DABZ. DABZ was far more effectively activated by hamster hepatocytes than by rat hepatocytes. This was not found with MABZ. Both substrates were poorly activated by guinea pig hepatocytes.

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The assessment of the potential carcinogenicity of a chemical requires a systematic approach taking into account various types of data. Important information on the DNA reactivity and other genetic effects of chemicals can be obtained from a battery of cellular tests. A battery is described which includes DNA repair in hepatocytes, mutagenesis in Salmonella typhimurium, mutagenesis, chromosome alterations, and transformation in mammalian cells. The interpretation of findings in this battery for the identification of potential carcinogenicity of chemicals is discussed.
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1986, Mutation Research/Environmental Mutagenesis and Related Subjects
This paper describes some striking differences between isolated human and monkey hepatocytes in their capacity to activate some known genotoxic agents into products mutagenic towards Salmonella typhimurium.
Isolated monkey hepatocytes, in contrast to human hepatocytes, appeared to activate benzidine (BZ), N-acetylbenzidine (MABZ), N,N′-diacetylbenzidine (DABZ), 2-aminofluorene (2-AF) and 2-acetylaminofluorene (2-AAF) poorly. With monkey hepatocytes BZ was slightly more mutagenic than DABZ, whereas with human hepatocytes DABZ was more active than BZ. N-Nitrosodimethylamine (DMN) and N-nitrosodiethylamine (DEN) were also found to be poorly mutagenic when activated by monkey hepatocytes, unlike the human hepatocytes. However, the polycyclic arylhydrocarbons benzo[a]pyrene (B[a]P) and 7,12-dimethylbenzanthracene (7,12-DMBA) were highly active in the presence of monkey hepatocytes, unlike the human hepatocytes. A metabolic study showed that monkey liver preparations seem to possess a higher monooxygenase activity towards B[a]P than human liver preparations.
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The mutagenicity of 10 known genotoxic compounds, of several chemical classes, was measured in Salmonella typhimurium mutagenicity assays comprising isolated human hepatocytes or human liver 9000 × g supernatant (S9)from 4 different individuals, as activating system.
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Comparison of the mutagenicity data obtained with the human liver preparations, with those obtained with rat liver preparations, showed great interspecies differences in the capacity to activate certain chemicals into mutagens.
The use of human liver preparations, in particular isolated human hepatocytes, may be of great value in studies on inter- and intraspecies variations in metabolic activation of genotoxic agents.
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Metabolic activation of N-acetylbenzidine and N, N′-diacetylbenzidine to mutagens, using isolated hepatocytes and the 9000 × g liver supernatant from rat, hamster and guinea pig

Abstract

Toxicology

Biochem. Pharmacol.

Toxicol. Lett.

Toxicol. Appl. Pharmacol.

Mutation Res.

Cancer Lett.

Exp. Cell. Res.

High yield preparation of isolated rat liver parenchymal cells

J. Cell. Biol.

Metabolism and pharmacokinetics of benzidine and its congeners in man and animal

Drug. Metab. Rev.