Comparison of primary hepatocytes and S9 metabolic activation systems for the C3H-10T 1/2 cell transformation assay

Three metabolic activation systems, primary rat hepatocytes, primary mouse hepatocytes and Aroclor 1254-induced rat liver S9 fraction were examined as exogenous activation systems for the C3H-10T 1/2 cell transformation assay. Under the conditions of the assay the primary mouse hepatocytes were more effective than the rat S9 fraction in mediating the transformation of C3H-10T 1/2 cells by the antineoplastic drug cyclophosphamide. However, the S9 fraction was more consistent than the mouse hepatocytes in the activation of dimethylnitrosamine. The primary rat hepatocytes were ineffective for activating either cyclophosphamide or dimethylnitrosamine in the transformation of C3H-10T 1/2 cells. The presence of mouse hepatocytes, but not the S9 fraction, inhibited transformation of C3H-10T 1/2 cells by 3-methylcholanthrene. These results demonstrate that the three systems were differentially effective in the activation of procarcinogens.