The activation of procarcinogens to mutagens by cultured rat hepatocytes in the L5178Y/TK mutation assay

Abstract

Whole cell preparations derived from collagenase-treated rat liver were cocultivated overnight with stationary (non-shaking) cultures of L5178Y/TK+/- cells in the presence of 8 different chemicals selected as representative aromatic amine, polycyclic hydrocarbon, or nitrosamine procarcinogens. When tested in the presence of hepatocytes, 2-aminoanthracene, 2-aminofluorene, N-nitrosodimethylamine, N-nitrosodiethylamine, N-nitrosodipropylamine, 3-methylcholanthrene, and benzo[a]pyrene all produced substantial dose-dependent increases in trifluorothymidine-resistant variants compared to solvent controls after 20 h total exposure time. Only N-nitrosodipropylamine (DPrN) and N-nitrosodiethylamine (DEN) produced any dose-related mutagenic activity in similar experiments where hepatocytes were omitted; however, the response for the DPrN was quite variable at high doses in the absence of hepatocytes and the mutagenic response for the DEN was consistently enhanced at all dose levels by the presence of hepatocytes. Benzanthracene was not active in the presence of whole hepatocytes, even when tested with cells from a rat pretreated 24 h earlier with 20 mg/kg benzanthracene. Excepting benzanthracene, these data suggest that rat hepatocytes can be used to active 3 types of procarcinogens to mutagens in the L5178Y/TK gene mutation assay.