BIOALKYLATION IN CHEMICAL CARCINOGENESIS

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The objectives of this biochemical research are to explore the role and regulation of bioalkylation in the activation of PAHs in chemical carcinogenesis. The bioalkylation substitution reaction of PAHs, consists of a biochemical reaction between certain unsubstituted PAHs and S-adenosyl-L-methionine (SAM) that is catalyzed by cytosolic enzymes. The introduction of the alkyl group takes place in the reactive meso-anthracenic positions or L- region. The rate and extent of the bioalkylation reaction of anthracene, benz(a)anthrcene, benzo(a)pyrene, anthanthrene and pyrene will be measured in cytosol preparations of rat liver, lung and subcutaneous tissue. Although some evidence for bioalkylation of PAHs in vivo has already been obtained, it is obviously desirable to quantitate both the rate and extent of this new biochemical reaction with SAM and without added SAM for comparison with in vitro studies. In contrast to most studies in this field this alternative pathway of activation by soluble enzymes does not involve microsomal reactions but is entirely concerned with the biochemical reactions that occur in cytosol preparations that are essentially free of microsomes. An intimately associated biological oxidation of the hydrocarbon also occurs in cytosol preparations and studies that are designed to determine the mechanism of the oxidation will also be undertaken in collaboration with Dr. Lauren Tolbert. The biosynthetic products of these cytosolic reactions will be identified by HPLC and GC/MS in most cases by comparison with authentic reference compounds. Carcinogenic activity will be determined in rats by subcutaneous injection of the PAH with and without other compounds that may enhance or inhibit carcinogenic activity. The isolation and characterization of specific end products of reaction of the cytosolic metabolites and model ultimate metabolites with macromolecules in vivo will be explored.