Toxicity of 20 Chemicals from the MEIC Programme Determined by Growth Inhibition of L-929 Fibroblast-like Cells.

The Multicentre Evaluation of In vitro Cytotoxicity (MEIC) programme is an international project aimed at evaluating the relevance of in vitro tests in predicting human toxicity. We have screened 20 chemicals (MEIC codes 31-50) from the programme, by using a cytotoxicity test based on growth inhibition of the mouse fibroblast-like L-929 cell line. Inhibition of cell growth was determined by the neutral red uptake method, which is well established and is used for screening the cytotoxicity of chemicals and plastics for pharmaceuticals and medical devices. The concentrations causing 50% inhibition of cell growth after a 72-hour exposure period varied from 3.1μM for hexachlorophene, to 1.4mM for caffeine. This is within the same range as results recently obtained with five other cell models. However, with some chemicals (chloroform, carbon tetrachloride and dichloromethane), no reliable results were obtained. These substances could not be dissolved in a reproducible way in any of the solvents used and, furthermore, they were highly volatile, which led to difficulties in maintaining the concentrations.