title: E- and Z-10-hydroxylation of nortriptyline by human liver microsomes--methods and characterization.
abstract: To enable in vitro characterization of nortriptyline 10-hydroxylase activity of microsomal fractions of human liver, methods for the determination of E- and Z-10-hydroxynortriptyline were developed. High performance liquid chromatography (HPLC) with UV-detection or HPLC separation followed by quantitation by gas chromatography-mass spectrometry were used. The microsomal 10-hydroxylation of nortriptyline was linear to 60 min with a protein concentration of 1 mg x ml-1. In 15 human livers a 5-fold variation in activity was found. The formation of the Z-isomer comprised 13 +/- 3% (mean +/- SD) of the total 10-hydroxylase activity. The 10-hydroxylation was inhibited by debrisoquine, sparteine, propranolol, and encainide. No effect or a stimulation of the activity was seen with p-nitroanisole and acetanilide.
mesh_terms: D000328:Adult; D000368:Aged; D003577:Cytochrome P-450 Enzyme System / Q000378:metabolism; D005260:Female; D006801:Humans; D006900:Hydroxylation; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D008875:Middle Aged; D009661:Nortriptyline / Q000378:metabolism*; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: D003577:Cytochrome P-450 Enzyme System; D009661:Nortriptyline