Cytotoxic activity and transformation of BALB/c 3T3 cells in vitro by the insecticide acephate

Cytotoxic and cell transforming activity of the organophosphate insecticide acephate have been studied in an in vitro experimental model which foresees the exposure of BALB/c 3T3 cells to the chemical. The assay was performed in the presence or absence of metabolic activation system derived from phenobarbital and β-naphthoflavone induced rats (S9-mix). Cytotoxicity of acephate was unaffected by the presence of the metabolizing fraction. Cell-transforming potential, evidenced through the induction of transformation foci, was observed at all tested doses (i.e. 100, 200 and 400 μg/ml) with or without exogenous bioactivation. This activity was related with cell proliferation since it was particularly evident in a level-II cell-transformation assay when the cells were allowed to perform active proliferative activity. These findings, obtained in a medium-term (6–8 weeks) test, may contribute to a better understanding of the action of acephate in the multistep carcinogenesis, proving more information on the oncogenic risk to humans.