The use of sister-chromatid exchange in Chinese hamster primary lung cell cultures to measure genotoxicity

Abstract

Primary cell cultures derived from Chinese hamster lung (CHL) were established, and their response for the induction of sister-chromatid exchange (SCE) by direct- and indirect-acting mutagens was characterized. An increase in SCE frequency was induced in CHL cells by 3-methylcholanthrene (MCA), benzo[ a]pyrene (BaP), and 2-aminoanthracene (2AA). The SCE frequency increased slightly after exposure to cyclophosphamide, but did not respond to the hepatocarcinogen dimethylnitrosamine (DMN). A slight increase in SCE frequency by DMN was observed in the CHL system with use of Aroclor-1254-induced rat liver homogenate fraction (S9). This response to DMN in CHL cells was lower than that seen when CHO cells were the target in the presence of S9. At low (1) and high (20) passages, the CHL cells responded with a similar dose-related increase in SCE frequency to direct- (ethyl methanesulfonate, EMS) and indirect- (MCA) acting mutagens. This response indicates that even after prolonged culturing in vitro, the cells retained the ability to metabolically activate xenobiotic promutagens. The induction of SCE by MCA occurred at concentrations that also induced macromolecular binding. SCE induction was also examined in primary lung cell cultures from animals exposed by nose-only inhalation to MCA aerosol. A significant increase in SCE frequency above controls was observed in cells from animals after a single exposure to MCA. No detectable increase in SCE frequency was observed after repeated inhalation exposures. Because CHL cells are of lung origin and showed metabolic activity, the CHL system appears to be appropriate for study of the genotoxic potential of inhaled compounds.