Sensitivity of the rat liver microsomal oxidation of pyrazole to antibody raised against the ethanol-inducible rabbit liver cytochrome P-450 isozyme.
Pyrazole is oxidized to 4-hydroxypyrazole by rat liver microsomes in a cytochrome P-450-dependent reaction and this oxidation can be increased by prior treatment of rats with pyrazole, 4-methylpyrazole, or chronic ethanol feeding. The induction pattern suggests that pyrazole may be an effective substrate for oxidation by P-450 IIE.1. This P-450 isozyme is recognized by antibody (anti-3a IgG) raised against the ethanol-inducible P-450 in rabbits. Experiments were carried out to evaluate the ability of anti-3a IgG to inhibit pyrazole oxidation by microsomes from controls and from rats treated with inducers of P-450 IIE.1. Immunoblots with anti-3a IgG or with the anti-pyrazole P-450 IgG were identical and indicated increased staining of the pyrazole P-450 with microsomes from rats treated with pyrazole, 4-methylpyrazole, or ethanol, relative to saline controls; very little staining occurred with microsomes from pair-fed controls or phenobarbital-treated rats. Rates of pyrazole oxidation were highest with microsomes from rats treated with the inducers of P-450 IIE.1 and lowest with pair-fed controls or rats treated with phenobarbital. Anti-3a IgG produced about a 60% decrease of pyrazole oxidation in microsomes from rats treated with inducers of P-450 IIE.1 and about a 25% decrease with the saline controls; no inhibition was found with microsomes from the phenobarbital-treated rats. The anti-3a IgG-resistant rate of pyrazole oxidation was similar with all the microsomal preparations, and was not due to interaction of pyrazole with hydroxyl radicals.(ABSTRACT TRUNCATED AT 250 WORDS)
Clejan
L A
LA
Department of Biochemistry, Mount Sinai School of Medicine, New York, NY 10029.
Koop
D R
DR
Cederbaum
A I
AI
D000818:Animals; D015153:Blotting, Western; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis / Q000276:immunology*; D004790:Enzyme Induction / Q000187:drug effects; D000431:Ethanol / Q000494:pharmacology*; D007074:Immunoglobulin G / Q000276:immunology; D007527:Isoenzymes / Q000096:biosynthesis / Q000276:immunology; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism*; D010084:Oxidation-Reduction; D011720:Pyrazoles / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D007074:Immunoglobulin G; D007527:Isoenzymes; D011720:Pyrazoles; D000431:Ethanol; C014606:4-hydroxypyrazole; D003577:Cytochrome P-450 Enzyme System