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

• Published in: Molecular pharmacology 2003-03, Vol.63 (3), p.532-537
• Main Authors: Ohtsuki, Sumio, Takizawa, Takuya, Takanaga, Hitomi, Terasaki, Nobuyuki, Kitazawa, Takeo, Sasaki, Masako, Abe, Takaaki, Hosoya, Ken-ichi, Terasaki, Tetsuya
• Format: Article
• Language: English
• Subjects: Animals; Biological Transport; Blood - metabolism; Cerebrospinal Fluid - metabolism; Choroid Plexus - cytology; Epithelial Cells - metabolism; Estrone - analogs & derivatives; Estrone - metabolism; Immunohistochemistry; Male; Oocytes - metabolism; Organic Anion Transporters, Sodium-Independent - biosynthesis; Organic Anion Transporters, Sodium-Independent - genetics; Organic Anion Transporters, Sodium-Independent - metabolism; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; Tritium; Xenopus laevis
• ISSN: 0026-895X; 1521-0111
• DOI: 10.1124/mol.63.3.532

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 μM 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, γ-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 μM 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.