Assessment of chemical toxicity using mammalian mitochondrial electron transport particles.

New spectrophotometric bioassay procedures have been developed for evaluating chemical toxicity, using electron transport particles isolated from bovine heart mitochondria, based on the ability of many toxic chemicals to interfere with the integrated function of electron transport enzymes. The sensitivity of the mitochondrial assay is compared to published sensitivities of other in vivo and in vitro toxicity testing methods. Regression analysis of logarithmically transformed toxicity values for 42 chemicals, including 8 pesticides, 5 drugs, 6 metals, 8 alcohols, 5 respiratory inhibitors, 4 phenols, and 2 phthalates, indicates excellent correlation between the sensitivity of the new assays and the sensitivity of mammalian cytotoxicity studies (r2 = 0.86). Data from aquatic exposure toxicity tests conducted in fish are also highly correlated with the mitochondrial assay results (r2 = 0.79). However, correlation of data from these methods with median lethal dose studies conducted in rats is not as good because of the inability of in vitro and aquatic exposure analyses to account for the gastrointestinal absorption, hepatic metabolism, and excretion processes which modify toxic responses following oral administration.