Functional changes in rat liver mitochondria on administration of 2-methyl-4-dimethylaminoazobenzene

1. Administration of 2-methyl-4-dimethylaminobenzene in the diet (0.1%, w/w) for 85-90 days doubled the content of mitochondria in the livers of rats. The azodye was covalently bound to liver proteins, and about 15% of the amount found in liver was associated with the mitochondrial fraction. 2. Mitochondria isolated from the livers of azodye-fed animals showed drastically lowered ability to oxidize NAD⁺-linked substrates. The inhibted electron-transfer step was the reduction of ubiquinone. The organelles showed a large increase in succinate oxidase activity. 3. The activity of cytochrome oxidase and the content of cytochrome aa₃ were substantially higher in these organelles. 4. Azodye-fed animals showed depressed serum cholesterol concentrations. The content of ubiquinone in liver also registered a small increase.