Research Product

This research program was initiated with the overall objective of determining the role of NADPH-dependent microsomal mono-oxygenase in the metabolism of the widespread environmental carcinogen benzo(a)pyrene (BP) by the oyster Crassostrea virginica. This enzyme system is important in detoxifying various xenobiotics and in activating polycyclic aromatic hydrocarbon oncogens as BP. A sensitive radioisotopic system was developed to permit the quantification of alkali-soluble and water-soluble BP metabolites produced by oyster mono-oxygenase. An NADPH- and O2-dependent aryl hydrocarbon hydroxylase (AHH) was shown to be located in the digestive glands of these bivalves associated with the microsomal subcellular fraction. The specific activity of oyster AHH was considerably lower than that of laboratory mice, but was consistently demonstrable. The BP metabolites produced were primarily water-soluble derivatives. There was some indication that oyster AHH was induced by chronic exposure of the animals to the environmental carcinogens BP and 3-methyl-cholanthrene. There was strong evidence that exposure to polychlorinated biphenyls (PCB) caused AHH induction. High-pressure liquid chromatography was used to identify BP metabolites produced by oyster AHH. The generation of various dihydrodiol, quinone, and hydroxy BP derivatives was shown; this production was augmented in PCB-exposed oysters. This report covers the period from July 1, 1976 to June 30, 1977, and work was completed as of August 31, 1977.