Evaluation of Electrochemiluminescent Metabolic Toxicity Screening Arrays Using a Multiple Compound Set

Abstract

Arrays for screening metabolite-generated toxicity utilizing spots containing DNA, enzyme, and electroluminescent (ECL) polymer ([Ru(bpy)₂PVP₁₀]²⁺) were extended to include a fully representative set of metabolic enzymes from human and rat liver microsomes, human and rat liver cytosol, and mouse liver S9 fractions. Array use involves two steps: (1) enzyme activation of the test chemical and metabolite reaction with DNA, and then, (2) capture of ECL resulting from DNA damage using a charge coupled device (CCD) camera. Plots of ECL increase vs enzyme reaction time monitor relative rates of DNA damage and were converted into turnover rates for enzymic production of DNA-reactive metabolites. ECL turnover rates were defined by R, the initial slope of ECL increase versus enzyme reaction time normalized for amounts of enzyme and test chemical. R-values were used to establish correlations for 11 toxic compounds with the standard toxicity metrics rodent liver TD₅₀ and lethal dose (LD₅₀), Ames tests, and Comet assays for in vitro DNA damage. Results support the value of the ECL genotoxicity arrays together with toxicity bioassays for early screening of new chemicals and drug candidates.