The primary objectives of the proposed research are to investigate the effects of reduced antioxidant defense mechanism(s), in this case vitamin E deficiency, selenium deficiency and a combination of each, on the metabolism of benzy(a)Pyrene-7,8-dihydrodiol (BP-7,8-diol) via the prostaglandin synthetase, and microsomal lipid peroxidation-mediated cooxidation in the rat lung. The hypothesis to be tested is that dietary vitamin E and selenium can prevent the generation of extremely reactive electrophilic intermediates, which may be mutagenic and/or carcinogenic, from BP-7,8-diol during cyclooxygenase and microsomal lipid peroxidation-dependent cooxidation. The proposed experiments will be conducted with mature male rats fed on chemically defined, purified diets with documented deficiencies of vitamin E, selenium or both. The specific experimental tasks addressed in this proposal include 1) the determination of in vitro lipid peroxidation potential of lung microsomes, 2) the measurement of in vitro binding to protein and DNA of BP-7,8-diol metabolites derived from cyclooxygenase and lipid peroxidation-dependent cooxidation, 3) the analysis and quantitation of BP-7,8-diol metabolites formed in the prostaglandin synthetase and lipid peroxidation-dependent reactions and 4) an assessment of the effects of purified selenium-dependent and selenium-independent-glutathione peroxidases on in vitro binding of BP-7,8-diol metabolites to protein and DNA. The research methods to be employed include spectrophotometric and isotope assays for measurment of enzyme activities, and liquid scintillation spectrometry, thin-layer, and high pressure liquid-chromatographic techniques for the analysis of BP-7,8-diol metabolites. From the information obtained in these studies insight will be gained to the understanding of the precise mechanism(s) by which vitamin E and selenium might protect the lung against tumors induced by the prostaglandin synthetase-mediated cooxidation of chemical carcinogens. Our long-term objectives are to investigate the synergistic effects of oxidate stress such as ozone exposure on the induction of lung cancer by environmental chemical carcinogens and the protective mechanism(s) of dietary vitamin E and selenium supplementation.
