Metabolic Activation of Carcinogens and Toxic Chemicals

1 The spatial parameters and electronic structures of 100 exogenous and endogenous chemicals have been determined by computer graphics, from which their oxidative metabolism by the cytochromes P-448 (activation) or the other families of cytochromes P-450 (generally detoxication) have been predicted. 2 The spatial parameters of these chemicals primarily determine the family of cytochrome P-450 by which the chemicals are metabolized and the electronic structures primarily determine their ease of oxidative metabolism. 3 The role of oxidative metabolism of xenobiotics by the cytochromes P-448, and their binding to the cytosolic Ah receptor, are considered in relationship to the mechanisms of chemical toxicity, mutagenicity, carcinogenicity, and co-carcinogenicity. 4 The mechanisms of chemical toxicity and carcinogenesis are considered in respect of activation through cytochrome P-448-mediated, conformationally-hindered oxygenation to reactive intermediates which, unlike most cytochrome P-450-oxygenated metabolites, are not acceptable substrates for conjugation and detoxication and therefore react with essential intracellular macromolecules. 5 The computer graphic method of determining the molecular conformations and electronic structures of molecules is a rapid, scientifically-based procedure for evaluation of the potential toxicity, mutagenicity and carcinogenicity of chemicals.