Mutagenic activation of aromatic amines by a human hepatoma cell (Hep G2) supernatant tested by means of Salmonella typhimurium strains with different acetyltransferase activities.

The study was carried out to characterize hepatoma cells (Hep G2) as activation system relevant to man and to investigate which are the tester strains most suitable for the mutagenic assay of aromatic amines. A supernatant prepared from the human hepatoma cell line Hep G2 was used to activate benzidine, 2-aminofluorene (2-AF) and 2-acetylaminofluorene (2-AAF) in the Salmonella typhimurium reversion assay. Activation by Hep G2 supernatant was studied with increasing concentrations of the three compounds, in tester strains TA98, YG1024, DJ400 and DJ460. Benz[alpha]anthracene (BA) pretreatment of cells increases the mutagenicity of benzidine in strains YG1024, DJ460 and DJ400. Activation of 2-AAF and 2-AF was observed in strains YG1024, DJ400 and, at the highest tested dose, in DJ460. These results were compared with those obtained with S9 from control and Aroclor 1254 (Aro)-pretreated rat liver. With strain TA98 comparable responses were obtained except for 2-AF which was better activated using rat liver S9. The use of strain YG1024 greatly increases the sensitivity of the response. Strain DJ460 makes it possible to detect activation of 2-AF and 2-AAF by Aro-induced rat liver. These results indicate that Hep G2 supernatant is a useful metabolic activation system of human origin that can be used to replace rat liver S9. An appropriate choice of the Salmonella strain not only can increase the sensitivity of the response, but may also help to overcome certain metabolic shortcomings of the Hep G2 cell line and rat liver S9.

Metabolic activation by a supernatant from human hepatoma cells: a possible alternative in mutagenic tests.

The supernatant from human Hep G2 hepatoma cells was examined for typical enzymatic activities involved in the metabolism of xenobiotics. Neither cytochrome P-450 nor b5 was detectable, but associated enzymatic activities were found especially after induction with hydrocortisone (HC) and benzanthracene (BA) suggesting that this Hep G2 supernatant contains cyt P-450 IA1 and IA2. Other critical enzymes are also present, but, as expected, at lower activities than in Aroclor 1254 rat liver S9, except for NADH and NADPH cytochrome c reductase. Results of the Ames test indicate that the induced Hep G2 supernatant is a suitable activator for the evaluation of genotoxicity of indirect mutagens.