Linked Life Data

10086984

Source:http://linkedlifedata.com/resource/pubmed/id/10086984

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
1
pubmed:dateCreated
1999-4-21
pubmed:abstractText
The aim of this study was to evaluate the (3S)-3-hydroxylation and the N-oxidation of quinidine as biomarkers for cytochrome P-450 (CYP)3A4 activity in human liver microsome preparations. An HPLC method was developed to assay the metabolites (3S)-3-hydroxyquinidine (3-OH-Q) and quinidine N-oxide (Q-N-OX) formed during incubation with microsomes from human liver and from Saccharomyces cerevisiae strains expressing 10 human CYPs. 3-OH-Q formation complied with Michaelis-Menten kinetics (mean values of Vmax and Km: 74.4 nmol/mg/h and 74.2 microM, respectively). Q-N-OX formation followed two-site kinetics with mean values of Vmax, Km and Vmax/Km for the low affinity isozyme of 15.9 nmol/mg/h, 76.1 microM and 0.03 ml/mg/h, respectively. 3-OH-Q and Q-N-OX formations were potently inhibited by ketoconazole, itraconazole, and triacetyloleandomycin. Isozyme specific inhibitors of CYP1A2, -2C9, -2C19, -2D6, and -2E1 did not inhibit 3-OH-Q or Q-N-OX formation, with Ki values comparable with previously reported values. Statistically significant correlations were observed between CYP3A4 content and formations of 3-OH-Q and Q-N-OX in 12 human liver microsome preparations. Studies with yeast-expressed isozymes revealed that only CYP3A4 actively catalyzed the (3S)-3-hydroxylation. CYP3A4 was the most active enzyme in Q-N-OX formation, but CYP2C9 and 2E1 also catalyzed minor proportions of the N-oxidation. In conclusion, our studies demonstrate that only CYP3A4 is actively involved in the formation of 3-OH-Q. Hence, the (3S)-3-hydroxylation of quinidine is a specific probe for CYP3A4 activity in human liver microsome preparations, whereas the N-oxidation of quinidine is a somewhat less specific marker reaction for CYP3A4 activity, because the presence of a low affinity enzyme is demonstrated by different approaches.
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0022-3565
pubmed:author
pubmed:issnType
Print
pubmed:volume
289
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
31-7
pubmed:dateRevised
2008-11-21
pubmed:meshHeading
pubmed-meshheading:10086984-Algorithms, pubmed-meshheading:10086984-Anti-Arrhythmia Agents, pubmed-meshheading:10086984-Antibodies, pubmed-meshheading:10086984-Binding Sites, pubmed-meshheading:10086984-Cytochrome P-450 CYP3A, pubmed-meshheading:10086984-Cytochrome P-450 Enzyme System, pubmed-meshheading:10086984-Enzyme Inhibitors, pubmed-meshheading:10086984-Humans, pubmed-meshheading:10086984-Hydroxylation, pubmed-meshheading:10086984-Immunochemistry, pubmed-meshheading:10086984-Isoenzymes, pubmed-meshheading:10086984-Ketoconazole, pubmed-meshheading:10086984-Kinetics, pubmed-meshheading:10086984-Microsomes, Liver, pubmed-meshheading:10086984-Mixed Function Oxygenases, pubmed-meshheading:10086984-Models, Biological, pubmed-meshheading:10086984-Oxidation-Reduction, pubmed-meshheading:10086984-Quinidine, pubmed-meshheading:10086984-Saccharomyces cerevisiae
pubmed:year
1999
pubmed:articleTitle
In vitro metabolism of quinidine: the (3S)-3-hydroxylation of quinidine is a specific marker reaction for cytochrome P-4503A4 activity in human liver microsomes.
pubmed:affiliation
Department of Clinical Pharmacology, Institute of Medical Biology, Odense University, Denmark. t.nielsen@winsloew.ou.dk
pubmed:publicationType
Journal Article, In Vitro