title: In vitro study of the functional expression of organic anion transporting polypeptide 3 at rat choroid plexus epithelial cells and its involvement in the cerebrospinal fluid-to-blood transport of estrone-3-sulfate.
abstract: The cerebrospinal fluid-to-blood efflux transport of estrone-3-sulfate (E(1)S) via the blood-cerebrospinal fluid barrier (BCSFB) may play an important role in regulating E(1)S levels in the brain. Here, we investigated the efflux transport of E(1)S at the BCSFB using conditionally immortalized rat choroid plexus epithelial cells (TR-CSFB) and identified the responsible transporter. The [(3)H]E(1)S uptake by TR-CSFB cells was composed of saturable and nonsaturable components, and the K(m) and V(max) values of the saturable component were determined to be 16.8 +/- 5.1 microM and 12.3 +/- 2.3 pmol/min/mg of protein, respectively. [(3)H]E(1)S uptake was inhibited by probenecid, cholate, taurocholate, sulfobromophthalein, dehydroepiandrosterone sulfate, triiodothyronine, thyroxin, and digoxin but not by p-aminohippuric acid, gamma-aminobutyric acid, or methotrexate, suggesting the involvement of organic anion transporting polypeptide (oatp) in the uptake. Reverse transcription-polymerase chain reaction analysis revealed that oatp3 was expressed in TR-CSFB cells and isolated rat choroid plexus, although oatp1 was not detected in either. Xenopus laevis oocytes expressing oatp3 exhibited [(3)H]E(1)S uptake activity with a K(m) of 8.09 +/- 2.83 microM and V(max) of 8.02 +/- 0.87 pmol/h/oocyte. Moreover, oatp3 is localized at the brush-border membrane of choroid plexus epithelial cells. These results suggest that oatp3 is involved in the E(1)S efflux transport at the BCSFB.
authors.affiliation: Department of Molecular Biopharmacy and Genetics, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, Japan.
authors.forename: Sumio
authors.initials: S
authors.lastname: Ohtsuki
authors.forename: Takuya
authors.initials: T
authors.lastname: Takizawa
authors.forename: Hitomi
authors.initials: H
authors.lastname: Takanaga
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Terasaki
authors.forename: Takeo
authors.initials: T
authors.lastname: Kitazawa
authors.forename: Masako
authors.initials: M
authors.lastname: Sasaki
authors.forename: Takaaki
authors.initials: T
authors.lastname: Abe
authors.forename: Ken-ichi
authors.initials: K
authors.lastname: Hosoya
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Terasaki
mesh_terms: D000818:Animals; D001692:Biological Transport; D001769:Blood / Q000378:metabolism*; D002555:Cerebrospinal Fluid / Q000378:metabolism*; D002831:Choroid Plexus / Q000166:cytology*; D004847:Epithelial Cells / Q000378:metabolism*; D004970:Estrone / Q000031:analogs & derivatives* / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D009865:Oocytes / Q000378:metabolism; D029362:Organic Anion Transporters, Sodium-Independent / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014316:Tritium; D014982:Xenopus laevis
chemical_list: D029362:Organic Anion Transporters, Sodium-Independent; C421102:Slco1a1 protein, rat; C421143:Slco1a5 protein, rat; D014316:Tritium; D004970:Estrone; C017296:estrone sulfate