Modulation of Phase II Drug Metabolizing Enzyme Activities by N-Heterocycles
Drugs and other chemicals that contain one or more heterocyclic nitrogen atoms are most widely known for their ability to both inhibit and induce cytochrome P450s. Their ability to affect a wide range of Phase II drug metabolizing enzyme activities has received much less attention and exposure. For some N-heterocycles, induction of Phase II metabolism occurs in the absence of induction effects on cytochrome P450, a property with potential utility in reducing drug and chemical toxicity (chemoprotection). The mechanism of this induction, and an accounting of the Phase II selectivity, has not been rigorously investigated. This review gathers and documents existing information on the simultaneous inductive effects of N-heterocycles on glucuronidation, sulfation (sulfonation) and glutathione conjugation reactions, as well epoxide hydrolase and quinone oxidoreductase activities. Basic information on cytochrome P450 induction is provided for comparative purposes. The review will serve as a base for any future interest in the phenomenon. The existing information on enzyme changes derives largely from laboratory animal studies. Chemicals investigated range from both simple and complex pyridines and imidazoles to benzoquinolines and phenanthrolines. Isomeric differences can have a major impact on induction characteristics and Phase II selectivity. Promising indications for the effectiveness of N-heterocycle elicited enzyme changes in chemoprotection in vivo awaits investigation.
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Document Type: Review Article
Publication date: December 1, 2002
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- Current Drug Metabolism aims to cover all the latest and outstanding developments in drug metabolism and disposition. The journal serves as an international forum for the publication of timely reviews in drug metabolism. Current Drug Metabolism is an essential journal for academic, clinical, government and pharmaceutical scientists who wish to be kept informed and up-to-date with the latest and most important developments. The journal covers the following areas:
In vitro systems including CYP-450; enzyme induction and inhibition; drug-drug interactions and enzyme kinetics; pharmacokinetics, toxicokinetics, species scaling and extrapolations; P-glycoprotein and transport carriers; target organ toxicity and interindividual variability; drug metabolism and disposition studies; extrahepatic metabolism; phase I and phase II metabolism; recent developments for the identification of drug metabolites and adducts.
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