The toxicity of allyl alcohol and several glycols (ethylene glycol, 1,2-propanediol, 1,3-propanediol, methoxyethanol, and the glycol ether dioxane) was studied in cultures of 3T3 cells and in co-cultures of 3T3 cells with microcarrier-attached hepatocytes. Metabolism-mediated effects on the cytotoxicity to 3T3 cells were recorded by differences in the growth of the cultures exposed in the presence or absence of hepatocytes. Hepatocyte viability was determined by depletion of intracellular lactate dehydrogenase and effects on the biotransformation ability of hepatocytes were assessed by determination of O-deethylation of 7-ethoxycoumarin (EOD activity). Allyl alcohol was the only substance more toxic to the hepatocytes than to 3T3 cells cultured in the absence of hepatocytes. Toxicity to 3T3 cells of allyl alcohol, ethylene glycol, and 1,3-propanediol, but not of 1,2-propanediol, methoxyethanol and dioxane, was markedly enhanced when the cells were co-cultured with hepatocytes. The results indicate that the toxicity of allyl alcohol, ethylene glycol, and 1,3-propanediol, to 3T3 cells depends on the formation of active metabolites. For ethylene glycol and 1,3-propanediol, growth of 3T3 cells in co-cultures was reduced at concentrations without effects on hepatocyte viability. Co-culture of 3T3 cells with microcarrier-attached rat hepatocytes represents a suitable approach for the in vitro evaluation of metabolism-mediated cytotoxicity.
Evaluation of equilibrium constants for the interaction of lactate dehydrogenase isoenzymes with reduced nicotinamide-adenine dinucleotide by affinity chromatography