caa a22 4500 477056563 CHVBK 20180405111347.0 cr unu---uuuuu 170330e19960901xx s 000 0 eng 10.1007/s002280050164 doi (NATIONALLICENCE)springer-10.1007/s002280050164 Interindividual variability in catalytic activity and immunoreactivity of three major human liver cytochrome P450 isozymes [Elektronische Daten] [C. Transon, S. Lecoeur, T. Leemann, P. Beaune, P. Dayer] Objective: Interindividual variations in immunoreactivity and function of three major human drug metabolising P450 monooxygenases has been investigated in liver microsomes from 42 Caucasians (kidney donors or liver biopsies). Methods: Diclofenac 4′-hydroxylation, dextromethorphan O-demethylation and midazolam 1′-hydroxylation, measured by HPLC in incubates, were used as probes to determine CYP2C9, CYP2D6 and CYP3A4 function kinetics, respectively. Immunoquantification of the three isoforms was achieved by Western blotting, using rabbit polyclonal antibodies raised against human CYP2C9 and human CYP3A4, and mouse monoclonal antibody raised against human CYP2D6. Results: Diclofenac 4′-hydroxylation exhibited Michaelis-Menten kinetics with kM= 3.4 μmol ⋅l−1 and Vmax = 45 nmole ⋅mg−1P ⋅h−1. Relative immunoreactivity of CYP2C9 was correlated with Vmax and CLint. Dextromethorphan O-demethylation in EM (extensive metabolisers) liver microsomes also showed Michaelis-Menten kinetics, with kM = 4.4 μmol ⋅l−1 and Vmax = 5.0 nmol ⋅mg−1P ⋅h−1. Relative immunoreactivity of CYP2D6 was correlated with Vmax and CLint. Midazolam 1′-hydroxylation also exhibited Michaelis-Menten kinetics with kM = 3.3 μmol ⋅l−1 and Vmax = 35 nmol ⋅mg−1P ⋅h−1. Relative immunoreactivity of CYP3A4 was correlated with Vmax and CLint. Immunoreactivity and function were correlated for each isozyme, but there was no cross correlation between isozymes. Conclusion: The velocity of metabolite formation (Vmax) by the three major human drug metabolising P450 monooxygenases is correlated with their immunoreactivity in liver microsomes. Interindividual variation was much larger for Vmax than kM. Interindividual variability was more pronounced for CYP2D6, probably due to the presence of several different functional alleles in the population of extensive metabolisers. Springer-Verlag Berlin Heidelberg, 1996 Key words Drug metabolism nationallicence human liver microsomes nationallicence interindividual variability nationallicence CYP2C9 nationallicence CYP2D6 nationallicence CYP3A4 nationallicence immunoreactivity nationallicence catalytic activity nationallicence cytochrome P450 nationallicence Transon C. Division of Clinical Pharmacology, University Hospitals, 24, rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland, CH aut Lecoeur S. INSERM U75, CHU-Necker, Paris, France, FR aut Leemann T. Division of Clinical Pharmacology, University Hospitals, 24, rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland, CH aut Beaune P. INSERM U75, CHU-Necker, Paris, France, FR aut Dayer P. Division of Clinical Pharmacology, University Hospitals, 24, rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland, CH aut https://doi.org/10.1007/s002280050164 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s002280050164 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Transon C. Division of Clinical Pharmacology, University Hospitals, 24, rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland, CH aut NATIONALLICENCE 700 1- Lecoeur S. INSERM U75, CHU-Necker, Paris, France, FR aut NATIONALLICENCE 700 1- Leemann T. Division of Clinical Pharmacology, University Hospitals, 24, rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland, CH aut NATIONALLICENCE 700 1- Beaune P. INSERM U75, CHU-Necker, Paris, France, FR aut NATIONALLICENCE 700 1- Dayer P. Division of Clinical Pharmacology, University Hospitals, 24, rue Micheli-du-Crest, CH-1211 Geneva 14, Switzerland, CH aut Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer