Abstract
Interindividual variability in protein expression of organic anion-transporting polypeptides (OATPs), OATP1B1, OATP1B3, OATP2B1, and multidrug resistance -linked P-glycoprotein (P-gp) or ABCB1 was quantified in frozen human livers (n=64) and cryopreserved human hepatocytes (n=12) by a validated LC-MS/MS method. Membrane isolation, sample workup and LC-MS/MS analyses were as described before by our laboratory. Briefly, total native membrane proteins, isolated from the liver tissue and cryopreserved hepatocytes, were trypsin digested and quantified by LC-MS/MS using signature peptide(s) unique to each transporter. The mean ± SD (maximum/minimum range in parentheses) protein expression (fmol/µg of membrane protein) in human liver tissue was, OATP1B1: 2.0±0.9 (7), OATP1B3: 1.1±0.5 (8), OATP2B1: 1.7±0.6 (5), and P-gp: 0.4±0.2 (8). Transporter expression in the liver tissue was comparable to that in the cryopreserved hepatocytes. Most importantly, livers with SLCO1B1 (encoding OATP1B1) haplotypes *14/*14 and *14/*1a (i.e., representing SNPs, c.388A>G, and c.463C>A), had significantly higher (P<0.0001) protein expression than the reference haplotype (*1a/*1a). Based on these genotype-dependent protein expression data, we predicted (using Simcyp) up to ~40% decrease in mean area under the curve (AUC) of rosuvastatin or repaglinide in those individuals harboring these variant alleles compared with those harboring the wild-type alleles. SLCO1B3 (encoding OATP1B3) SNPs did not significantly affect protein expression. Age and sex were not associated with transporter protein expression. These data will facilitate prediction of population-based human transporter-mediated drug disposition, drug-drug interactions, and interindividual variability through PBPK modeling.
- ABC transporters
- genetic polymorphism
- hepatobiliary transport
- mass spectrometry
- p-glycoprotein
- pharmacogenomics
- physiologically-based pharmacokinetics
- The American Society for Pharmacology and Experimental Therapeutics