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Aim:Imrecoxib is a novel and moderately selective COX-2 inhibitor.The aim ofthe present in vitro investigation was to study the formation of the major metabo-lite 4′-carboxylic acid imrecoxib(M2)and identify the enzyme(s)involved in thereaction.Methods:The formation of M2 was studied in rat liver cytosol in theabsence or presence of liver microsomes.The formed metabolite was identifiedand quantified by LC/MS~n.In addition,to characterize the cytochrome P450(CYP)isozymes involved in M2 formation,the effects of typical CYP inhibitors(such asketoconazle,quinine,α-naphthoflavone,methylpyrazole,and cimetidine)on theformation rate of M2 were investigated.Results:The formation of M2 from 4’-hydroxymethyl imrecoxib(M4)was completely dependent on rat liver microsomesand NADPH.Enzyme kinetic studies demonstrated that the formation rate of M2conformed to monophasic Michaelis-Menten kinetics.Additional experimentsshowed that the formation of M2 was induced significantly by dexamethasoneand lowered by ketoconazole strongly and concentration-dependently.Bycomparison,other CYP inhibitors,such as α-naphthoflavone,cimetidine,quinine,and methylpyrazole had no inhibitory effects on this metabolic pathway.Conclusion:These biotransformation studies of M4 and imrecoxib in rat liver atthe subcellular level showed that the formation of M2 occurs in rat liver microsomesand is NADPH-dependent.The reaction was mainly catalyzed by CYP 3A inuntreated rats and in dexamethasone-induced rats.Other CYP,such as CYP 1A,2C,2D,and 2E,seem unlikely to participate in this metabolic pathway.
Aim: Imrecoxib is a novel and moderately selective COX-2 inhibitor. The aim of the present in vitro investigation was to study the formation of the major metabo-lite 4’-carboxylic acid imrecoxib (M2) and identify the enzyme (s) involved in Thereaction. Methods: The formation of M2 was studied in rat liver cytosol in the presence or presence of liver microsomes. The formed metabolite was identified and quantified by LC / MS ~ n. addition, to characterize the cytochrome P450 (CYP) isozymes involved in M2 formation of the effects of typical CYP inhibitors (such as ketoconazole, quinine, α-naphthoflavone, methylpyrazole, and cimetidine) was investigated. Results: The formation of M2 from 4’-hydroxymethyl imrecoxib rat liver microsomes and NADPH. Enzyme kinetic studies that that formation rate of M2conformed to monophasic Michaelis-Menten kinetics. Additional experiment show that the formation of M2 was induced significantly by dexamethasoneand lo wered by ketoconazole strongly and concentration-dependently. Bycomparison, other CYP inhibitors, such as α-naphthoflavone, cimetidine, quinine, and methylpyrazole had no inhibitory effects on this metabolic pathway. Confluence: These biotransformation studies of M4 and imrecoxib in rat liver atthe subcellular level showed that the formation of M2 occurs in rat liver microsomesand is NADPH-dependent. The reaction was mainly catalyzed by CYP 3A in untreated rats and in dexamethasone-induced rats. Other CYP, such as CYP 1A, 2C, 2D, and 2E, seem unlikely to participate in this metabolic pathway