title: Unique properties of NADPH- and NADH-dependent metabolism of p-nitroanisole catalyzed by cytochrome P-450 isozyme 2 in pulmonary and hepatic microsomal preparations from rabbits.
abstract: Approximately 90% of the NADPH- and NADH-dependent O-demethylation of p-nitroanisole (PNA) in the hepatic microsomal fraction from phenobarbital (PB)-treated rabbits and in the pulmonary microsomal fraction from untreated rabbits is catalyzed by the same isozyme of cytochrome P-450. This isozyme of cytochrome P-450 catalyzes less than 60% of this reaction in the hepatic microsomal fraction from untreated rabbits. Antibodies to NADPH-cytochrome P-450 reductase inhibit NADPH-dependent metabolism of p-nitroanisole by about 90% but have no effect on NADH-dependent metabolism. Hepatic NADPH-dependent metabolism of pNA and reduction of cytochrome c are inhibited to the same extent with varying amounts of antibodies to NADPH cytochrome P-450 reductase. The same relationship between inhibition of monooxygenase and reductase activities is observed for the hepatic and pulmonary metabolism of benzphetamine and 7-ethoxycoumarin. In contrast, the relationship between inhibition of the pulmonary NADPH-dependent metabolism of pNA and reductase activity is biphasic; at 75% inhibition of reductase activity, metabolism of pNA is inhibited by less than 25%. For NADH-dependent metabolism of pNA, our results indicate that both electrons are transferred to cytochrome P-450 from cytochrome b5.
mesh_terms: D000818:Animals; D000840:Anisoles / Q000378:metabolism*; D002248:Carbon Monoxide / Q000494:pharmacology; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism*; D003573:Cytochrome b Group / Q000378:metabolism; D015786:Cytochromes b5; D004579:Electron Transport; D007527:Isoenzymes / Q000378:metabolism; D008168:Lung / Q000201:enzymology*; D008297:Male; D008861:Microsomes / Q000201:enzymology; D008862:Microsomes, Liver / Q000201:enzymology; D009243:NAD / Q000378:metabolism; D009249:NADP / Q000378:metabolism; D010090:Oxidoreductases, O-Demethylating / Q000037:antagonists & inhibitors / Q000378:metabolism; D011817:Rabbits
chemical_list: D000840:Anisoles; D065607:Cytochrome P-450 Enzyme Inhibitors; D003573:Cytochrome b Group; D007527:Isoenzymes; D009243:NAD; D009249:NADP; D002248:Carbon Monoxide; D015786:Cytochromes b5; D003577:Cytochrome P-450 Enzyme System; C026048:4-nitroanisole O-demethylase; D010090:Oxidoreductases, O-Demethylating; C005306:4-nitroanisole