title: Human organic anion transporters function as a high-capacity transporter for p-cresyl sulfate, a uremic toxin.
abstract: BACKGROUND
  Recent clinical studies have shown that increased serum levels of p-cresyl sulfate (PCS), a uremic toxin, are associated with the progression of chronic kidney disease (CKD) and cardiovascular outcomes. Using rat renal cortical slices, we previously reported that the rat organic anion transporter (OAT) could play a key role in the renal tubular secretion of PCS. However, no information is currently available regarding the transport of PCS via human OAT (hOAT) isoforms, hOAT1 and hOAT3.
  
  
  METHODS
  Uptake experiments of PCS were performed using HEK293 cells, which stably express hOAT1 or hOAT3.
  
  
  RESULTS
  PCS was taken up by hOAT1/HEK293 and hOAT3/HEK293 cells in a time- and concentration-dependent manner. The apparent K m for the hOAT1-mediated transport of PCS was 128 μM, whereas in hOAT3/HEK293, saturation was not observed at the highest tested PCS concentration of 5 mM. Probenecid, an OAT inhibitor, inhibited PCS transport by hOAT1 and hOAT3. The uptake of p-aminohippurate by hOAT1 and estron-3-sulfate by hOAT3 was decreased with increasing PCS concentration. The apparent 50 % inhibitory concentrations for PCS were 690 and 485 μM for hOAT1 and hOAT3, respectively.
  
  
  CONCLUSIONS
  PCS is a substrate for hOAT1 and hOAT3, and hOAT1 and hOAT3 appear to play a physiological role as a high-capacity PCS transporter. Since hOATs are expressed not only in the kidneys, but also in blood vessels and osteoblasts, etc., these findings are of great significance in terms of elucidating the renal clearance, tissue disposition of PCS and the mechanism of its toxicity in CKD.
authors.affiliation: Department of Biopharmaceutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-ku, Kumamoto, 862-0973, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watanabe
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Sakaguchi
authors.forename: Ryusei
authors.initials: R
authors.lastname: Sugimoto
authors.forename: Ken-Ichi
authors.initials: K
authors.lastname: Kaneko
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Iwata
authors.forename: Shunsuke
authors.initials: S
authors.lastname: Kotani
authors.forename: Makoto
authors.initials: M
authors.lastname: Nakajima
authors.forename: Yu
authors.initials: Y
authors.lastname: Ishima
authors.forename: Masaki
authors.initials: M
authors.lastname: Otagiri
authors.forename: Toru
authors.initials: T
authors.lastname: Maruyama
mesh_terms: D003408:Cresols / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D027362:Organic Anion Transport Protein 1 / Q000378:metabolism*; D029362:Organic Anion Transporters, Sodium-Independent / Q000378:metabolism*; D013463:Sulfuric Acid Esters / Q000378:metabolism*; D014511:Uremia / Q000378:metabolism
chemical_list: D003408:Cresols; D027362:Organic Anion Transport Protein 1; D029362:Organic Anion Transporters, Sodium-Independent; D013463:Sulfuric Acid Esters; C114338:organic anion transport protein 3; C408690:4-cresol sulfate