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Benzo(a)pyrene was metabolized by the stomach and hepatopancreas of blue crabs (Callinectes sapidus). Microsomes from the stomach showed high aryl hydrocarbon hydroxylase (AHH) activity while those from the hepatopancreas showed low AHH activity, due to release of an AHH inhibitor during tissue extraction. Stomach microsomes, metabolized 14C-benzo(a)pyrene to a series of dihydrodiols, phenols, and quinones, including 9, 10-, 4, 5-, and 7, 8-dihydrodiol benzo(a)pyrene, 9-hydroxybenzo(a)pyrene, 3-hydroxybenzo(a)pyrene, and quinones. The major metabolite was 3-hy-droxybenzo(a)pyrene. Cytochrome P-450, one of the components of the AHH system, was found in microsomes of both stomach and hepatopancreas. The cell types found in the hepatopancreas were isolated and separated. Cytochrome P-450 was found in a mixture of F- and B-cells but was absent in R-cells. The F- and B-cells are thought to function in protein synthesis and enzyme secretion. One major and two minor forms of cytochrome P-450 were partially purified from blue crab hepatopancreas microsomes. The major form in a reconstituted enzyme system was active in oxidizing benzo(a)pyrene to a series of phenols and diols.
aquatic toxicology, benzo(a)pyrene, cytochrome P-450, mixed-function oxygenase, crabs, purification, reconstitution
Professor, Skidaway Institute of Oceanography, Savannah, GA