Comparison of the continuous rat hepatoma cell line 2sFou with primary rat hepatoyctes cultures for the induction of DNA repair synthesis by nitrosamines, benzo[<em>a</em>]pyrene and hydroxyurea.

Abstract

We have examined the suitability of the continuous rat hepatoma cell line 2sFou for testing the genotoxicity of chemicals in comparison with that of primary rat hepatocyte cultures (HPC). The capacity of the cells for metabolic activation was assessed by measuring induction of DNA-repair synthesis and inhibition of replicative DNA synthesis by the test compounds dimethylnitrosamine (DMN), diethylnitrosamine (DEN), hydroxyurea (HU) and benzo[a]pyrene (BaP), which are substrates for major hepatic and extrahepatic forms of cytochrome P-450 dependent monooxygenases. The cellular capacity for DNA-repair synthesis was assessed using UV-light as a DNA-damaging agent. Repair-specific incorporation of [3H]deoxycytidine (3H-dCyd) caused by UV-light was higher in 2sFou cells than in HPC. In contrast, background repair incorporation of 3H-dCyd in 2sFou cells was only 1/3 that found in HPC. All the test agents induced DNA repair and inhibited DNA synthesis in both 2sFou cells and HPC. The two nitrosamines were more effective in HPC than in 2sFou cells. HU and BaP affected DNA repair and DNA synthesis in the two cell systems at similar range of concentrations. In general, DNA repair in the 2sFou cells increased near linearly with the concentrations of the test compounds. The data indicate that 2sFou cells are capable of activating hepatotropic pro-mutagens/carcinogens such as dialkylnitrosamines, and are sensitive indicators of DNA damage. In contrast, BaP, a non-hepatotoxic compound, caused only little DNA repair in these cells. Thus, continuously growing cells, such as 2sFou, show a qualitatively similar response to genotoxic chemicals as HPC and offer a potential alternative to HPC for genotoxicity testing