title: Application of A. C.-polarography in a study of p-nitroanisole metabolism and its kinetic properties.
abstract: Phase sensitive alternating current polarography was introduced for the simultaneous determination of p-nitroanisole and its metabolites p-nitrophenol and p-nitrocatechol in kinetic studies with rat liver microsomes. The substrate p-nitroanisole disappears rather rapidly while p-nitrophenol is formed. First traces of a second oxidation product, p-nitrocatechol, can be detected only after a few minutes after the initiation of the reaction. This suggest that O-demethylation of p-nitroanisole is the primary reaction which is followed by aromatic ortho hydroxylation of p-nitrophenol. After incubation times longer than 15 minutes, appreciable amounts of p-nitrocatechol are found which shows optical absorption characteristics similar to those of p-nitrophenol (absorption maximum at 440 nm). It is concluded from these kinetic experiments that optical determination of the primary metabolite during the initial reaction phase constitutes a reliable measure of microsomal O-demethylation activity. Phenobarbital induction differentially increases O-demethylation and ring-ortho-hydroxylation activities. From this and respective inhibition studies it is concluded that possibly multiple forms of cytochrome P-450 are involved in the metabolism of either p-nitroanisole or p-nitrophenol.
mesh_terms: D000818:Animals; D000840:Anisoles / Q000378:metabolism*; D002396:Catechols / Q000378:metabolism; D003640:Dealkylation; D006900:Hydroxylation; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008797:Metyrapone / Q000494:pharmacology; D008862:Microsomes, Liver / Q000032:analysis / Q000187:drug effects / Q000378:metabolism; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009596:Nitrophenols / Q000378:metabolism; D010634:Phenobarbital / Q000494:pharmacology; D011048:Polarography; D011335:Proadifen / Q000494:pharmacology; D011506:Proteins / Q000032:analysis; D051381:Rats; D013997:Time Factors
chemical_list: D000840:Anisoles; D002396:Catechols; D009596:Nitrophenols; D011506:Proteins; D011335:Proadifen; D006899:Mixed Function Oxygenases; C005306:4-nitroanisole; D010634:Phenobarbital; D008797:Metyrapone