PT  - JOURNAL ARTICLE
AU  - Sumio Ohtsuki
AU  - Olaf Schaefer
AU  - Hirotaka Kawakami
AU  - Tae Inoue
AU  - Stephanie Liehner
AU  - Asami Saito
AU  - Naoki Ishiguro
AU  - Wataru Kishimoto
AU  - Eva Ludwig-Schwellinger
AU  - Thomas Ebner
AU  - Tetsuya Terasaki
TI  - Simultaneous Absolute Protein Quantification of Transporters, Cytochromes P450, and UDP-Glucuronosyltransferases as a Novel Approach for the Characterization of Individual Human Liver: Comparison with mRNA Levels and Activities
AID  - 10.1124/dmd.111.042259
DP  - 2012 Jan 01
TA  - Drug Metabolism and Disposition
PG  - 83--92
VI  - 40
IP  - 1
4099  - http://dmd.aspetjournals.org/content/40/1/83.short
4100  - http://dmd.aspetjournals.org/content/40/1/83.full
SO  - Drug Metab Dispos2012 Jan 01; 40
AB  - The purpose of the present study was to determine the absolute protein expression levels of multiple drug-metabolizing enzymes and transporters in 17 human liver biopsies, and to compare them with the mRNA expression levels and functional activities to evaluate the suitability of the three measures as parameters of hepatic metabolism. Absolute protein expression levels of 13 cytochrome P450 (P450) enzymes, NADPH-P450 reductase (P450R) and 6 UDP-glucuronosyltransferase (UGT) enzymes in microsomal fraction, and 22 transporters in plasma membrane fraction were determined using liquid chromatography/tandem mass spectrometry. CYP2C9, CYP2E1, CYP3A4, CYP2A6, UGT1A6, UGT2B7, UGT2B15, and P450R were abundantly expressed (more than 50 pmol/mg protein) in human liver microsomes. The protein expression levels of CYP3A4, CYP2B6, and CYP2C8 were each highly correlated with the corresponding enzyme activity and mRNA expression levels, whereas for other P450s, the protein expression levels were better correlated with the enzyme activities than the mRNA expression levels were. Among transporters, the protein expression level of organic anion-transporting polypeptide 1B1 was relatively highly correlated with the mRNA expression level. However, other transporters showed almost no correlation. These findings indicate that protein expression levels determined by the present simultaneous quantification method are a useful parameter to assess differences of hepatic function between individuals.