Metabolism of amitriptyline with CYP2D6 expressed in a human cell line.
1. Expressed human cytochrome P450 enzyme CPY2D6 was used to metabolize amitriptyline (AMI). It was established that CYP2D6 not only catalyzed ring 10-hydroxylation of AMI, but also mediated its N-demethylation to nortriptyline (NT), as well as the formation of 10-hydroxy-NT from NT. When the metabolism of AMI by CYP2D6 was repeated in the presence of quinidine, none of the metabolites, 10-hydroxy-AMI, NT and 10-hydroxy-NT, was formed. 2. Biochemical parameters of NT formation from AMI were determined, yielding Km = 47.48 +/- 1.32 microM; Vmax = 3.95 +/- 0.11 nmol/h/mg protein. The same parameters were calculated for the formation of 10-hydroxy-AMI (E + Z-isomers) from AMI, yielding Km = 10.70 +/- 0.20 microM; Vmax = 8.99 +/- 0.47 nmol/h/mg protein. 3. The formation of 10-hydroxy-NT from AMI proceeded primarily via NT and to a much lesser extent via 10-hydroxy-AMI. 4. Quantitative analyses of AMI and its metabolites were difficult to reproduce when the metabolites were analysed underivatized. Two derivatization procedures, acetylation and trifluoroacetylation, were employed to improve assay reproducibility.
Coutts
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Neurochemical Research Unit, Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada.
Bach
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Baker
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D000215:Acylation; D000639:Amitriptyline / Q000031:analogs & derivatives / Q000378:metabolism* / Q000493:pharmacokinetics; D000929:Antidepressive Agents, Tricyclic / Q000378:metabolism; D002460:Cell Line; D002849:Chromatography, Gas; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism*; D006801:Humans; D008861:Microsomes / Q000378:metabolism; D009661:Nortriptyline / Q000031:analogs & derivatives / Q000378:metabolism
D000929:Antidepressive Agents, Tricyclic; C013567:10-hydroxynortriptyline; D000639:Amitriptyline; D009661:Nortriptyline; D019389:Cytochrome P-450 CYP2D6; C033738:10-hydroxyamitriptyline