Abstract
Sandwich-cultured rat hepatocytes are used in drug discovery for pharmacological and toxicological assessment of drug candidates, yet their utility as a functional model for drug transporters has not been fully characterized. To evaluate the system as an in vitro model for drug transport, expression changes of hepatic transporters relative to whole liver and freshly isolated hepatocytes (day 0) were examined by real-time quantitative reverse transcription-polymerase chain reaction for 4 consecutive days of culture. No significant differences in transporter expression levels were observed between freshly isolated hepatocytes and whole liver. Two distinct mRNA profiles were detected over time showing 1) a more than 5-fold decline in levels of uptake transporters such as Na+-taurocholate cotransporting polypeptide (Ntcp), organic anion transporter (Oat) 2, organic anion-transporting polypeptide (Oatp) 1a1, Oatp1a4, and Oatp1b2 and 2) a greater than 5-fold increase of efflux transporters P-glycoprotein (P-gp), breast cancer resistance protein (Bcrp), and multidrug resistance-related proteins (Mrp) 1, 2, 3, and 4. In addition, protein levels and functional activities for selected transporters were also determined. Protein levels for Mrp2, Bcrp, P-gp, Ntcp, and Oatp1a4 corresponded to changes in mRNA. Functional activities of Oatps and Oct1 exhibited a 3- and 4-fold decrease on day 2 and day 4, respectively, relative to that on day 0, whereas a more than 10-fold reduction in Oat2 activity was observed. These results indicate that the cell culture conditions used herein did not provide an optimal environment for expression of all hepatic transporters. Significant time-dependent alterations in basal gene expression patterns of transporters were detected compared with those in liver or freshly isolated hepatocytes. Further work and new strategies are required to improve the validity of this model as an in vitro tool for in vivo drug transport or biliary clearance prediction.
Footnotes
This work was supported in part by National Institutes of Health National Heart, Lung, and Blood Institute [Training Grant T32-HL07013] (to J.S.H.).
Article, publication date, and citation information can be found at http://dmd.aspetjournals.org.
doi:10.1124/dmd.111.039545.
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The online version of this article (available at http://dmd.aspetjournals.org) contains supplemental material.
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ABBREVIATIONS:
- OATP/Oatp
- organic anion transporting polypeptide
- OCT/Oct
- organic cation transporter
- OAT/Oat
- organic anion transporter 2
- MRP/Mrp
- multidrug resistance-related protein
- P-gp
- P-glycoprotein
- BCRP/Bcrp
- breast cancer resistant protein
- E17BG
- estradiol 17β-d-glucuronide
- PAH
- p-aminohippuric acid
- MPP+
- 1-methyl-4-phenylpyridinium
- WEM
- Williams' E medium
- MDR/Mdr
- multidrug resistance protein
- Slc
- solute carrier organic transporter
- Bsep
- bile salt export pump
- NTCP/Ntcp
- Na+-taurocholate cotransporting polypeptide
- DPP IV
- dipeptidyl peptidase IV
- GAPDH
- glyceraldehyde-3-phosphate dehydrogenase
- ZO-1
- zonula occludens protein 1
- RT
- reverse transcription
- PCR
- polymerase chain reaction
- DAPI
- 4′,6′-diamidino-2-phenylindole
- PBS
- phosphate-buffered saline
- q
- quantitative
- OTF1
- POU domain, class 2, transcription factor 1.
- Received March 17, 2011.
- Accepted August 23, 2011.
- Copyright © 2011 by The American Society for Pharmacology and Experimental Therapeutics
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