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FIGURE 4. Uptake of iodide and perrhenate in hNIS-transfected MDCK cells. Error bars denote 1 SD. (A) Time course of uptake. Cells were incubated with 20 µmol/L iodide or perrhenate supplemented with carrier-free 125I- and 188ReO4-, respectively, for the indicated periods of time. Solid symbols represent uptake in NIS-transfected cells, and open symbols represent uptake in nontransfected cells. Uptake of iodide exceeds that of perrhenate at all time points in the transfected cells. Transfected cells in the presence of the potent NIS inhibitor perchlorate and non-NIS-transfected MDCK cells did not concentrate either anion. (B) Kinetic analysis of iodide and perrhenate uptake into hNIS-transfected MDCK cells based on 2-min uptake values at variable substrate concentrations. Vmax and Km values were estimated using the Marquard–Levenberg algorithm as 106 ± 3.2 and 24.6 ± 1.81 pmol/µg for iodide and 25.6 ± 1.4 and 4.06 ± 0.87 µmol/L for perrhenate (plotted symbols represent experimental data and solid lines the fitted curves).
