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Figure 2. Tranilast inhibits urate transport mediated by the human urate transporter GLUT9a. (A) Time course of [14C]‐urate uptake by control and GLUT9a‐expressing oocytes. Inset, western blot analysis of GLUT9a protein expressed in oocytes. (B) [14C]urate transport properties of GLUT9a: voltage sensitivity and Na+‐dependence was examined by replacing extracellular NaCl by KCl or LiCl. We also assessed [14C]‐urate uptake by GLUT9a in the absence of extracellular Cl− ion (0 Cl−); in 0 Cl− bath, NaCl was replaced by Na‐gluconate (Na‐Gluc), KCl by k‐gluconate (K‐Gluc), MgCl2 by Mg‐gluconate, and CaCl2 by Ca‐gluconate. Asterisk, P < 0.001 compared with NaCl (ND96); NS, not significant. (C) Inhibition of [14C]‐urate uptake by GLUT9a in the presence of antiuricosuric or uricosuric drugs: The uptake of [14C]‐urate (40 μmol/L) by GLUT9a‐expressing oocytes was determined in complete absence of Na+ (NaCl of ND96 medium was replaced by KCl) after 1 h in the absence or presence of inhibitors (uricosuric drugs) which were added to the extracellular medium (pH 7.4) at the indicated concentrations. *P < 0.001 compared with DMSO. (D) Inhibition of [14C]‐urate uptake by GLUT9a in depolarized cells. The uptake of [14C]‐urate (40 μmol/L) by GLUT9a‐expressing oocytes was determined in the complete absence of Na+ (NaCl of ND96 medium was replaced by KCl) after 1 h in the absence or presence of inhibitors (uricosuric drugs) at the indicated concentrations. *P < 0.001 compared with DMSO. Tran, Benz Prob, Sal, DMSO. Data are mean ± S.E. with n = 12–15. Data are mean ± S.E. with n = 12–15. (D) The 50% inhibitory concentration (IC 50) curve of tranilast for [14C]‐urate uptake via GLUT9a. Tran, tranilast; Benz, benzbromarone; Prob, probenecid; Sal, salicylate; DMSO, dimethylsulfoxide. Image published in: Mandal AK et al. (2017) © 2017 The Authors. This image is reproduced with permission of the journal and the copyright holder. This is an open-access article distributed under the terms of the Creative Commons Attribution license Larger Image Printer Friendly View

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