A COMPARATIVE-STUDY OF THE TOXICITY OF CHEMICALLY REACTIVE XENOBIOTICS TOWARDS ADHERENT CELL-CULTURES - SELECTIVE ATTENUATION OF MENADIONE TOXICITY BY BUTHIONINE SULFOXIMINE PRETREATMENT

Metabolic activation to reactive intermediates is a prerequisite for m any forms of chemically-induced toxicity. Hepa 1c1c-9 cells were expos ed to varying concentrations of several reactive metabolites implicate d in adverse drug reactions and the toxicity of the compounds assessed using applied fluorescence technology. Cytotoxicity was assessed usin g the fluorescence of ,7'-bis-(2-carboxyethyl)-5-(6)-carboxy-fluoresce in as an index of cell viability. The role of glutathione in cellular defence against these chemicals was investigated by pretreating the ta rget cells overnight with buthionine sulphoximine, a specific inhibito r of glutathione synthesis. Depletion of intracellular glutathione aug mented the toxicity of N-acetyl-p-benzoquinone imine (1.5-3-fold at 10 0 and 10 mum). Toxicity produced by the hydroxylamine of sulphamethoxa zole (500 mum) was dependent entirely on pretreatment of the cells wit h buthionine sulphoximine (% cell death = 33 +/- 16 compared with 0 +/ - 4 in untreated cells, P < 0.05). By contrast, the lethal effects of the model quinone, menadione, were attenuated markedly following gluta thione depletion. The data obtained suggest that this assay, previousl y used with suspension cultures, may be useful in the rapid in-vitro s creening of putative reactive intermediates. Moreover, the application of such methodology should prove beneficial for the elucidation of ce llular mechanisms of defence and detoxification.