Cytotoxicity of the MEIC reference chemicals in rat hepatoma-derived Fa32 cells

The cytotoxicity of the MEIC reference chemicals was investigated in rat hepatoma-derived Fa32 cells. The total protein content was measured as an endpoint after exposure times of 30 min and 24 h, both in normal and glutathione-depleted cells. The neutral red uptake inhibition and the MTT conversion were also measured after 30 min. On average, the cytotoxicity was higher in glutathione-depleted cells when compared to normal cells, and was lower after 30 min than after 24 h. Evidence was obtained for lysosomal attack (of five chemicals) or mitochondrial dysfunction (of six chemicals) as the primary intoxication mechanism. Malathion and mercuric chloride belong to both series of chemicals. Good to excellent correlations were observed when the 50% inhibitory concentrations of the six different in vitro assays were compared. When the six in vitro assays in Fa32 cells were compared with the human toxicity, the correlation coefficient was almost always identical to that obtained previously in human hepatoma-derived Hep G2 cells. The latter was the best acute in vitro assay for the prediction of human toxicity within the MEIC study. Altogether the results integrate very well with the basal cytotoxicity concept (Ekwall, B., 1995. The basal cytotoxicity concept. In: Goldberg, A.M., Van Zutphen, L.F.M. (Eds.), The World Congress on Alternatives and Animal Use in the Life Sciences: Education, Research, Testing. Mary Ann Liebert Publishers, New York, pp. 721-725).