Monoclonal antibody-directed characterization of benzene, ethoxyresorufin and pentoxyresorufin metabolism in rat liver microsomes.
The contribution of cytochrome P450IA, P450IIB, P450IICII and P450IIEI to the oxidative metabolism of benzene, 7-ethoxyresorufin and 7-pentoxyresorufin was investigated using monoclonal antibodies (MAb) in liver microsomes from fed, one-day fasted, phenobarbital (PB)-, 3-methylcholanthrene (MC)- and ethanol-treated rats. Overall catalytic activity varied with different pretreatments and thereby the contribution of different P450s. MAb 1-91-3 against P450IIE1 did not influence alkoxyresorufin dealkylation but inhibited benzene aromatic hydroxylase (BAH) in relation to its increasing inducibility as follows: MC, PB (less than or equal to 48%) less than fed (less than or equal to 59%) less than fasted (less than or equal to 70%) less than ethanol (less than or equal to 91%). MAbs 2-66-3, 4-7-1 and 4-29-5, all against P450IIB, had no effect on 7-ethoxyresorufin O-deethylase (EROD) but inhibited the activities of high-Km BAH (greater than or equal to 58%) and 7-pentoxyresorufin O-depentylase (PROD) (greater than or equal to 96%) in PB-treated microsomes. MAb 1-7-1 against P450IA inhibited EROD (79%), PROD (50%) and high-Km BAH (42%) activities in MC-microsomes. MAb 1-68-11 against P450IIC11 inhibited EROD, PROD and high-Km BAH activities. Thus, P450IIE1 contributed to benzene metabolism as a low-Km BAH but not to alkoxyresorufin metabolism. P450IIB was responsible besides for the major part of 7-pentoxyresorufin metabolism also, selectively, for benzene hydroxylation at high benzene concentrations. P450IA contributed primarily to 7-ethoxyresorufin metabolism and only slightly to PROD and high-Km BAH activities. P450IIC11 contributed slightly to high-Km BAH and to alkoxyresorufin metabolism.
Department of Hygiene, Shinshu University School of Medicine, Matsumoto, Japan.
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T
Nakajima
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E
Elovaara
S S
SS
Park
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HV
Gelboin
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E
Hietanen
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H
Vainio
D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology*; D001554:Benzene / Q000378:metabolism*; D019363:Cytochrome P-450 CYP1A1; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D000431:Ethanol / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D008748:Methylcholanthrene / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology / Q000378:metabolism*; D006899:Mixed Function Oxygenases / Q000037:antagonists & inhibitors; D010078:Oxazines / Q000378:metabolism*; D010088:Oxidoreductases / Q000037:antagonists & inhibitors; D010634:Phenobarbital / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D000911:Antibodies, Monoclonal; D065607:Cytochrome P-450 Enzyme Inhibitors; D007527:Isoenzymes; D010078:Oxazines; D000431:Ethanol; D008748:Methylcholanthrene; C007649:ethoxyresorufin; C044943:pentoxyresorufin; D003577:Cytochrome P-450 Enzyme System; D006899:Mixed Function Oxygenases; D010088:Oxidoreductases; C019765:benzene 1,2-dioxygenase; D019363:Cytochrome P-450 CYP1A1; D001554:Benzene; D010634:Phenobarbital