Antioxidants such as t-butylated hydroxytoluene (BHT) and t-butylated hydroxvanisol (BHA) are known to retard the incidence of chemical carcinogenesis induced by polycyclic aromatic hydrocarbons in mouse lung and forestomach. Although the mechanism underlying the biological effect of these compounds is not clear, the antineoplastic effect of antioxidants may be due to the induction of enzymes such as glutathione (GSH) S-transferases which are involved in the detoxification of activated carcinogens. In rodents, hepatic GSH S-transferases are induced by BHA and BHT. We propose to study the effect of these compounds on various GSH S-transferases and other GSH-linked detoxification systems in rat and mouse lung. The effect of antioxidants on the individual isoenzymes of GSH S-transferase in mouse and rat lung will be studied. These isoenzymes will be purified to homogeneity from rodent and human lung and the structural, functional and genetic interrelationship among various isoenzymes will be studied. In order to delineate their role in the detoxification of the activated carcinogens the binding characteristics of the isoenzymes with the activated carcinogens and the substrate specificities of individual isoenzymes will be studied. The activated carcinogens will be prepared in vitro by the action of the enzymes of microsomal oxygenase system on benzo(a)pyrene. Antibodies raised against individual isoenzymes will be used to localize the enzymes in specific cell types of lung by immunofluorescence techniques. We have demonstrated that administration of BHA and BHT causes significant elevation of GSH levels in rodent liver and lung. Therefore, the effect of antioxidants on enzymes of glutathione biosynthesis, degradation and the enzymes of mercapturic acid pathway will be studied. The physiological significance of GSH-peroxidase activity expressed by some of the forms of GSH S-transferases, particularly by the membrane bound (microsomal) GSH S-transferase, will be studied. In addition, the role of GSH S-transferases in conjugating GSH to the endogeneously generated products of lipid peroxidation and the effect of antioxidants on some of the key enzymes of microsomal oxygenase system such as epoxide hydratase will be studied. These studies will greatly help in achieving the overall objective of developing means and ways to prevent chemical carcinogenesis caused by environmental agents.