Abstract
The aim of this study was to quantitatively determine the constitutive expression levels of various transporter mRNAs in rat choroid plexus. To provide a reference for the relative expression levels, the expression of various transporter mRNAs in choroid plexus were compared with that in liver, kidney, and ileum. The mRNA levels of multidrug resistance protein (Mrp)1, 2, 3, 4, 5, and 6; multidrug resistance (Mdr)1a, 1b, and 2; organic anion transporting polypeptide (Oatp)1, 2, 3, 4, 5, 9, 12, and Oat-K (1/2); organic anion transporter (Oat)1, 2, and 3; organic cation transporter (Oct)1, 2, 3, N1, and N2; bile acid transporters sodium taurocholate cotransporting polypeptide (Ntcp), bile salt excretory protein (Bsep), and ileal bile acid transporter (Ibat); divalent metal transporter 1 (DMT1), Menke's and Wilson's metal transporters; equilibrative nucleotide transporters (Ent) 1 and 2, and constitutive nucleotide transporters (Cnt)1 and 2; peptide transporters (Pept)1 and 2; as well as ATP-binding cassette (Abc)G5 and 8 were measured in choroid plexus by the branched DNA signal amplification method. Mrp1, 4, and 5, Oatp3, Menke's transporter, DMT1, Ent1, and Pept2 mRNAs were expressed in choroid plexus at higher levels than in liver, kidney, or ileum. OctN1 and N2, Oatp2, Oat2 and 3, and Cnt1 and 2 mRNAs expressions were detectable in choroid plexus, but the levels were lower compared with that in liver, kidney, or ileum. The remaining transporters [Mrp2, Mrp3, Oct1, Oct2, Oatp1, Oatp4, Oatp5, Oatp12, Oat-K (1/2), Ntcp, Bsep, Ibat, Mdr1a, Mdr1b, Mdr2, Oat1, Ent2, Pept1, AbcG5, AbcG8] were expressed at very low levels in choroid plexus. The constitutive expression levels of different transporters in choroid plexus may provide an insight into the range of xenobiotics that can potentially be transported by the choroid plexus, thereby providing a means of xenobiotic detoxification in the brain.
Footnotes
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↵1 Present Address: U.S. Food and Drug Administration, CFSAN/OFAS/DBGNR, 5100 Paint Branch Parkway, HFS-255, College Park, MD 20740.
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↵2 These authors contributed equally to this work
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↵3 Abbreviations used are: ABC, ATP-binding cassette; bDNA, branched DNA; Mrp, multidrug resistance protein; Mdr, multiple drug resistance; Oatp, organic anion transporting polypeptide; Oat-K, organic anion transporter K; Oct, organic cation transporter; Ntcp, sodium taurocholate cotransporting polypeptide; DMT1, divalent metal transporter 1; Ent, equilibrative nucleoside transporter; Cnt, concentrative nucleoside transporter; Pept, peptide transporter; Ibat, ileal bile acid transporter; RLU, relative luminescence unit(s); CP, choroid plexus; CNS, central nervous system; P-gp, P-glycoprotein; CSF, cerebrospinal fluid; RT-PCR, reverse transcription-polymerase chain reaction; PCG, benzylpenicillin; DCT1, divalent cation transporter1.
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This work was supported by National Institutes of Health Grant ES-09716. This work was conceived of and performed entirely at the University of Kansas Medical Center. Opinions expressed in this article are authors' personal opinion and they do not reflect U.S. Food and Drug Administration's opinion.
- Received May 12, 2003.
- Accepted August 12, 2003.
- The American Society for Pharmacology and Experimental Therapeutics
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