Fig. 3. Dependence of taurine uptake on [Na⁺] and [Cl^-] in mussel taurine transporter (muTAUT)-injected oocytes. Taurine uptake was measured at (A) various Na⁺ (1-250 mmol l^-1) concentrations and constant Cl^- concentration (250 mmol l^-1) or (B) various Cl^- (1-250 mmol l^-1) concentrations and constant Na⁺ concentration (250 mmol l^-1), with 10 µmol l^-1 taurine containing 0.5 µCi ml^-1 [³H]taurine. Isotonicity of the medium was maintained with choline chloride or sodium gluconate. Plotted data were adjusted by subtraction of uptake values by water-injected oocytes from those by muTAUT-injected oocytes (N=6-8). Error bars represent the standard deviation. The Hill coefficient and K₅₀ were estimated by linear fitting of Hill plots (insets).