title: Inhibition and induction of cytochrome P450 isozymes after repetitive administration of imipramine in rats.
abstract: Repetitive oral administration of imipramine (100 mg/kg/day for 5 days) caused a decrease in rat liver microsomal debrisoquine 4-hydroxylase activity, a characteristic reaction catalyzed by cytochrome P450 (CYP) 2D1. Other CYP2D-dependent reactions (such as bunitrolol 4-hydroxylation, lidocaine 3-hydroxylation, and propranolol 4-, 5- and 7-hydroxylations) were also impaired by the treatment, but not those catalyzed by other CYP isozymes. Imipramine pretreatment did not change the immunochemically determined content of the CYP2D protein, suggesting that CYP2D is inactivated. Imipramine pretreatment also resulted in an increase in total CYP content and in formation of a ferrous CYP metabolic intermediate (MI)-complex absorbing at 454 nm. Although the total CYP content was increased by the treatment of these microsomes with ferricyanide to dissociate the MI-complex, the CYP2D-dependent activities were not restored, suggesting that the MI-complex was not the primary cause of CYP2D inhibition. This pretreatment regimen caused marked increases in immunochemically determined levels of CYP2A1, CYP2B1, CYP2B2, CYP2C6, and CYP3A2, and in the activities of 2 alpha-, 2 beta-, 6 beta-, 7 alpha-, 16 alpha-, and 16 beta-hydroxylation and 17-oxidation of testosterone. These results indicate that imipramine has two actions on the liver CYP system (i.e. as an inhibitor of the CYP2D enzyme and as a phenobarbital-type inducer).
authors.affiliation: Laboratory of Biopharmaceutics, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Masubuchi
authors.forename: C
authors.initials: C
authors.lastname: Takahashii
authors.forename: N
authors.initials: N
authors.lastname: Fujio
authors.forename: T
authors.initials: T
authors.lastname: Horie
authors.forename: T
authors.initials: T
authors.lastname: Suzuki
authors.forename: S
authors.initials: S
authors.lastname: Imaoka
authors.forename: Y
authors.initials: Y
authors.lastname: Funae
authors.forename: S
authors.initials: S
authors.lastname: Narimatsu
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D000929:Antidepressive Agents, Tricyclic / Q000494:pharmacology*; D019389:Cytochrome P-450 CYP2D6; D065607:Cytochrome P-450 Enzyme Inhibitors; D003577:Cytochrome P-450 Enzyme System / Q000096:biosynthesis* / Q000378:metabolism; D005292:Ferricyanides / Q000494:pharmacology; D007099:Imipramine / Q000494:pharmacology*; D015151:Immunoblotting; D007527:Isoenzymes / Q000037:antagonists & inhibitors* / Q000096:biosynthesis*; D008012:Lidocaine / Q000494:pharmacology; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000378:metabolism; D010084:Oxidation-Reduction; D011433:Propranolol / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013739:Testosterone / Q000378:metabolism
chemical_list: D000319:Adrenergic beta-Antagonists; D000929:Antidepressive Agents, Tricyclic; D065607:Cytochrome P-450 Enzyme Inhibitors; D005292:Ferricyanides; D007527:Isoenzymes; C007931:hexacyanoferrate III; D013739:Testosterone; D003577:Cytochrome P-450 Enzyme System; D008012:Lidocaine; D011433:Propranolol; D006899:Mixed Function Oxygenases; D019389:Cytochrome P-450 CYP2D6; C071864:bunitrolol 4-hydroxylase; D007099:Imipramine