Abstract
Multidrug-associated protein 2 (MRP2) is an efflux transporter that is expressed at the bile canalicular membrane. To allow in vitro to in vivo extrapolation of the contribution of MRP2 toward hepatic disposition of its substrates, data on the interindividual variability of hepatic MRP2 protein expression are required. Therefore, we quantified the expression of MRP2 in the University of Washington (UW) human liver bank (n = 51) using a modified version of a previously validated liquid chromatography/tandem mass spectrometry assay. An unlabeled (LTIIPQDPILFSGSLR) and stable isotope-labeled (LTIIPQDPILFSGSL[13C615N1]R) surrogate peptide for MRP2 were used as the calibrator and internal standard, respectively. After isolation of the membrane fraction from the liver tissue, in-solution tryptic digestion was conducted. Quality control samples created by spiking human serum albumin or pooled human liver (n = 51) matrix with three different MRP2 synthetic peptide concentrations generated error and precision values of less than 15%. As determined by the surrogate peptide, the average MRP2 expression in the UW liver bank samples was 1.54 ± 0.64 fmol/μg liver membrane protein and was found to be independent of age (7–63 years) or sex. A single nucleotide polymorphism in the promoter region (rs717620), previously thought to affect MRP2 expression, did not influence hepatic expression of MRP2. In contrast, the single nucleotide polymorphism 21214G>A (V417I; rs2273697) was associated with significantly higher hepatic MRP2 expression.
Footnotes
This work was supported by the National Institutes of Health National Institute of General Medical Sciences [Grant GM32165]; a grant from Pfizer Inc.; and the Drug Metabolism, Transport and Pharmacogenomic Research program of the School of Pharmacy.
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
ABBREVIATIONS:
- MRP2
- multidrug resistance-associated protein 2
- UW
- University of Washington
- LS/MS/MS
- liquid chromatography/tandem mass spectrometry
- HSA
- human serum albumin
- QC
- quality control
- SNP
- single nucleotide polymorphism
- SIL
- stable isotope label.
- Received November 9, 2011.
- Accepted February 8, 2012.
- Copyright © 2012 by The American Society for Pharmacology and Experimental Therapeutics
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