title: An improved assay of 7-ethoxycoumarin O-deethylase activity: induction of hepatic enzyme activity in C57BL/6J and DBA/2J mice by phenobarbital, 3-methylcholanthrene and 2,3,7,8-tetrachlorodibenzo-p-dioxin.
abstract: An improved in vitro fluorometric assay of the O-deethylation of 7-ethoxycoumarin which is at least 10 times more sensitive than existing methods is described. Nearly quantitative recovery of the product which is essentially free of fluorescent impurities is obtained by a simple two-step extraction procedure. In C57BL/6J mice O-deethylating activity was induced 3-fold by 3-methylcholanthrene and 7-fold by phenobarbital. Administration of phenobarbital resulted in a 10-fold stimulation of enzyme activity in DBA/2J mice. Kinetic analysis indicated that at least two and possibly more components are involved in the metabolism of 7-ethoxycoumarin. Differential stimulation of the maximal activities associated with these components was observed after the administration of phenobarbital, 3-methylcholanthrene, or 2,3,7,8-tetrachlorodibenzo-p-dioxin. The ED50 values for the induction by 2,3,7,8-tetrachlorodibenzo-p-dioxin of 7-ethoxycoumarin O-deethylase and aryl hydrocarbon hydroxylase activities in C57BL/6J mice were almost identical and approximately 10-fold less than in DBA/2J mice similarly treated.
mesh_terms: D000818:Animals; D001189:Aryl Hydrocarbon Hydroxylases / Q000096:biosynthesis; D003374:Coumarins; D004147:Dioxins / Q000494:pharmacology*; D004790:Enzyme Induction / Q000187:drug effects; D005019:Ethyl Ethers; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008748:Methylcholanthrene / Q000494:pharmacology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D010105:Oxygenases / Q000096:biosynthesis / Q000378:metabolism*; D010634:Phenobarbital / Q000494:pharmacology*; D000072317:Polychlorinated Dibenzodioxins / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence
chemical_list: D003374:Coumarins; D004147:Dioxins; D005019:Ethyl Ethers; D000072317:Polychlorinated Dibenzodioxins; D008748:Methylcholanthrene; D010105:Oxygenases; D001189:Aryl Hydrocarbon Hydroxylases; D010634:Phenobarbital