Cytotoxicity of the MEIC test chemicals in primary neurone cultures.

50 Multicentre Evaluation of In Vitro Cytotoxicity (MEIC) test chemicals were assayed for cytotoxicity in primary cultures of chick embryo forebrain neurones using the MTT and neutral red assays. The neutral red assay was consistently more sensitive to chemical toxicity; however, both assays were equally predictive when compared with in vivo toxicity data obtained from the Registry of Toxic Effects of Chemical Substances. High correlations were obtained when comparing the in vitro data with ip rodent toxicity data, but these correlations decreased significantly when oral toxicity data were used. The predictive value of the in vitro data for oral human toxicity was generally poor, but comparable with its value in predicting oral rodent toxicity. In a limited study with 10 of the MEIC test chemicals, the cytotoxicity of some compounds was dependent on the degree of differentiation of the neurone cultures, suggesting that this culture system may not only be sensitive to the basal cytotoxicity of chemicals, but also to toxic effects specific to the specialized differentiated functions of the central nervous system.