Cytokine-mediated production of nitric oxide in isolated rat hepatocytes is dependent on cytochrome P-450III activity.
To investigate the role of the cytochrome P-450 system in NO synthesis, cytochrome P-450IIIA, IIE and IA activities were specifically inhibited by cimetidine (IIIA), clotrimazole (IIIA), benzoflavone (IA) and disulfiram (IIE) in a model of cultured rat hepatocytes. Cytokine-induced NO synthesis was significantly decreased in the presence of cimetidine and clotrimazole. Kinetic analysis revealed a non-competitive mode of inhibition (Ki = 21 mM, cimetidine; Ki = 13 microM, clotrimazole). Reverse transcriptase-PCR and immunoblot analysis revealed no significant change in steady state levels of iNOS mRNA and protein expression with P-450IIIA inhibition. Purified iNOS enzyme activity was not altered. These data suggest that cytokine-mediated hepatocyte synthesis of NO is dependent upon P-450IIIA activity, which functions in a post-translational capacity.
Kuo
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PC
Department of Surgery, MSOB X300, Stanford University Medical Center, CA 94305.
Abe
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KY
D000594:Amino Acid Oxidoreductases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D002478:Cells, Cultured; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D016207:Cytokines / Q000494:pharmacology*; D017931:DNA Primers; D007527:Isoenzymes / Q000378:metabolism*; D008099:Liver / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009569:Nitric Oxide / Q000096:biosynthesis*; D019001:Nitric Oxide Synthase; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley
D065607:Cytochrome P-450 Enzyme Inhibitors; D016207:Cytokines; D017931:DNA Primers; D007527:Isoenzymes; D012333:RNA, Messenger; D009569:Nitric Oxide; D003577:Cytochrome P-450 Enzyme System; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases