FIGURE 8.

The properties of diuretics interaction on transport mediated by hNPT4_L. A and B, dose dependence of loop diuretic, bumetanide (A) and furosemide (B), inhibition on hNPT4_L-mediated [¹⁴C]PAH (10 μm) uptake. The 30-min uptake was determined in the presence of varying concentrations of bumetanide or furosemide in extracellular high potassium uptake solution (Na⁺ in the basal uptake solution was replaced by K⁺) (pH 7.4). The values were expressed as percentages of control condition (in the absence of diuretics), the values of water-injected oocytes were subtracted from that of hNPT4_L-expressing oocytes (n = 6). C, concentration dependence of hNPT4_L-mediated [³H]bumetanide uptake. The uptake was performed using hNPT4_L-expressing oocytes for 30 min in the extracellular high potassium concentration with varying bumetanide concentrations (0.1, 0.3, 1, 3, 10, 30, 100, 300, and 1000 μm) (pH 7.4). The Eadie-Hofstee plot is shown in the inset. The values are the means ± S.E., n = 6. D and E, the interaction of bumetanide (E) and furosemide (F) on hNPT4_L-mediated [¹⁴C]urate uptake. The oocytes were incubated in high potassium uptake solution in the presence of 250 μm [¹⁴C]urate with varying bumetanide or furosemide concentrations for 1.0 h. The uptake values (water-injected oocytes were subtracted) in the presence of varying concentrations of inhibitors were shown as percentages of the control value (no inhibitors). The values are the means ± S.E., n = 6.