Formation of reactive oxygen species in rat hepatoma-derived Fa32 cells to predict human toxicity

The cytotoxicity of the MEIC (Multicentre Evaluation of In vitro Cytotoxicity) reference chemicals was investigated by measuring the increased reactive oxygen species (ROS) formation in rat hepatoma-derived Fa32 cells. ROS formation was measured with 2',7'-dichlorodihydrofluorescein diacetate as a fluorescent probe. The results were quantified by determining the ROS50. This is the concentration of test compound required to increase the ROS formation with 50% compared with control cells. An extremely high ROS formation was observed with ferrous sulfate. Of a total of 44 chemicals, an increased ROS formation was observed for 24. This was not the case for the 20 other chemicals. When the ROS formation in Fa32 cells was compared with human toxicity, the correlation coefficient was clearly higher than for human hepatoma-derived Hep G2 cells, at least when the extremely sensitive ferrous sulfate was withdrawn from the comparison. The Hep G2 assay was the best acute in vitro assay for the prediction of human toxicity within the MEIC study. Consequently, the ROS formation assay in Fa32 cells has a high predictive value for human toxicity, with the drawback that only ROS increasing chemicals can be evaluated.