title: Functional cooperation of SMCTs and URAT1 for renal reabsorption transport of urate.
abstract: Urate is mainly excreted into urine in humans. Serum urate level is regulated by a urate transport system located on the renal proximal tubule. Urate transporter 1 (URAT1) is located on the apical side of the renal proximal tubule and is responsible for the reabsorption of urate from the luminal side into tubular cells. At the same site, it has been hypothesized that sodium-coupled monocarboxylate transporters (SMCTs) are responsible for the transportation of monocarboxylates such as lactate and nicotinate, which are exchanged for urate transport via URAT1. Accordingly, SMCTs could enhance URAT1-mediated urate reabsorption by providing monocarboxylates for the exchange. The present study was carried out to clarify the hypothesized functional cooperative relationship between URAT1 and SMCTs in the reabsorptive transport of urate. By preloading nicotinate in SMCT1/URAT1-coexpressing Xenopus oocytes, URAT1-mediated urate transport was stimulated. Nicotinate was taken up by SMCT1 but not by URAT1. When removing sodium ions from the uptake medium, the stimulation effect was decreased. When adding SMCT1 inhibitors, the stimulation effect was also reduced. The results from this study indicate the cooperative relationship of URAT1 and SMCT1, and that SMCT1 is a potential target for the alteration of renal handling of urate indirectly.
authors.affiliation: Department of Membrane Transport and Biopharmaceutics, Faculty of Pharmacy, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan.
authors.forename: Yang
authors.initials: Y
authors.lastname: Lu
authors.forename: Takeo
authors.initials: T
authors.lastname: Nakanishi
authors.forename: Ikumi
authors.initials: I
authors.lastname: Tamai
mesh_terms: D000818:Animals; D002087:Butyrates / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D019344:Lactic Acid / Q000494:pharmacology; D027501:Monocarboxylic Acid Transporters / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D009525:Niacin / Q000494:pharmacology; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism; D027361:Organic Anion Transporters / Q000819:agonists* / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D013997:Time Factors; D014527:Uric Acid / Q000378:metabolism*; D014981:Xenopus
chemical_list: D002087:Butyrates; D027501:Monocarboxylic Acid Transporters; D027361:Organic Anion Transporters; C103862:urate transporter; D009525:Niacin; D014527:Uric Acid; D019344:Lactic Acid; D012964:Sodium