Figure 2. SLC26A4 mediates Cl⁻/I⁻ and I⁻/HCO₃⁻ exchange.

In A and B, oocytes expressing SLC26A4 were incubated in Hepes-buffered, Cl⁻-free media and then exposed to Cl⁻-free media containing 3 (A) or 10 mm I⁻ (B) to measure Cl⁻_i/I⁻_o exchange. The black trace in A is control with water-injected oocytes. At the time period bordered by dashed lines the oocytes were incubated with Cl⁻- and I⁻-free media to test for I⁻_i/OH⁻_o exchange. Oocyte in A was then exposed to Cl⁻_o to measure I⁻_i/Cl⁻_o exchange and the oocyte in B was exposed to Cl⁻-free, HCO₃⁻-buffered media to measure I⁻_i/HCO₃⁻_o exchange (light grey portion of traces). C shows the mean ±s.e.m. of the indicated number of experiments. D compares the rates of HCO₃⁻_i/Cl⁻_o (dark trace) and HCO₃⁻_i/I⁻_o exchange (grey trace). Oocytes in HCO₃⁻-buffered media were incubated in Cl⁻-free media to deplete the oocytes of Cl⁻ and load them with HCO₃⁻ (see Fig. 1C). Then, the oocytes were exposed to HCO₃⁻-buffered media containing either 85 mm Cl⁻ or 85 mm I⁻. The histogram shows the mean ±s.e.m. of the indicated number of experiments.