A novel adrenocorticotropin-inducible cytochrome P450 from rat adrenal microsomes catalyzes polycyclic aromatic hydrocarbon metabolism.
7,12-Dimethylbenz(a)anthracene (DMBA) causes massive ACTH-dependent necrosis of the rat adrenal cortex. This may be related to an ACTH-inducible adrenal microsomal cytochrome P450 that metabolizes polycyclic aromatic hydrocarbons (PAH). The proportions of major monooxygenated products of rat adrenal microsomal DMBA metabolism (DMBA-8,9-diol, DMBA-3,4-diol, and DMBA-phenols) differ significantly from that of P450IA1, the most active PAH-metabolizing P450 in rat liver microsomes. After hypophysectomy, both DMBA metabolic activity and a 57K protein which is distinct from P450XXI disappear from rat adrenal microsomes. ACTH restores both 57K protein and DMBA metabolic activity in hypophysectomized rats almost to the levels in intact untreated rats, but not to levels in ACTH-induced intact rats. The 57K protein has been partially purified from solubilized microsomes in a single step, using detergent elution from a new HPLC matrix consisting of monolayers of phosphatidylcholine covalently bound to a silica support. The resulting P450 preparation contains a single major (57K) band, constituting approximately 70% of the total protein (specific content, 2 nmol P450/mg protein; turnover number, 1.5 nmol DMBA min-1. A rabbit polyclonal antibody raised against this preparation also recognizes a single ACTH-inducible 57K rat adrenal microsomal protein on immunoblots and dose-dependently inhibits DMBA metabolism in solubilized reconstituted rat adrenal microsomes. This 57K P450 is immunochemically distinct from rat P450s of the I, II, III, XVII, and XXI families, but it is immunochemically closely related to a 55K benz(a)anthracene-inducible P450 in the 10T1/2 mouse embryo fibroblast cell line.
Otto
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Department of Pharmacology, University of Wisconsin Medical School, Madison 53706.
Marcus
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Pidgeon
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Jefcoate
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D015127:9,10-Dimethyl-1,2-benzanthracene / Q000378:metabolism; D000311:Adrenal Glands / Q000187:drug effects / Q000201:enzymology / Q000648:ultrastructure*; D000324:Adrenocorticotropic Hormone / Q000494:pharmacology*; D000818:Animals; D015153:Blotting, Western; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000302:isolation & purification / Q000378:metabolism*; D004790:Enzyme Induction / Q000187:drug effects; D007016:Hypophysectomy; D008297:Male; D008861:Microsomes / Q000201:enzymology*; D008970:Molecular Weight; D011083:Polycyclic Compounds / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains
D011083:Polycyclic Compounds; D015127:9,10-Dimethyl-1,2-benzanthracene; D000324:Adrenocorticotropic Hormone; D003577:Cytochrome P-450 Enzyme System