The Use of Human Lymphocytes for the In Vitro Estimation of Acute Toxicity of Ten Chemicals from the MEIC List

Abstract

The acute cytotoxicity of ten chemicals included in the MEIC (multicentre evaluation of in vitro cytotoxicity) list has already been estimated in various cell lines, e.g. primary rat hepatocytes, HeLa cells, human hepatoma cells, and 3T3 and mouse fibroma cells. In the present study, primary cultures of human lymphocytes, with or without an S9-mix (microsomes), were used to assay for in vitro toxicity. The cultured cells were initially treated with different concentrations of the respective drugs for 24 hours. Then cellular enzymatic activity was estimated using two assay systems, namely, measurement of cytosolic LDH activity and the mitochondrial (diaphorase) MTT test. Since the biological significance of the assay of LC50 values is dependent upon the slope of the dose-response curves, the results are expressed as LC20, LC50 and LC80 values in μM for the ten drugs. A Spearman rank correlation analysis revealed a significant correlation between the results from the two assays in both cell culture systems (r=1.00 and r=0.99). The LC50 values found in the lymphocyte cultures, both with and without an S9-mix, correlated well with the results previously found using primary cultures of hepatocytes and HeLa cells.