Figure 6. SCN⁻ currents are blocked by external SO₄²⁻.

A and D, time course of current increases for rat prestin (A) and zebrafish prestin (D) upon removal of external SO₄²⁻. Current amplitudes were measured at repetitive voltage steps to +200 mV, and [SO₄²⁻] is given below the time dependence of the current amplitude. B, current–voltage relationships from cells transiently expressing SLC26A5 (RAT)/prestin in solutions with varying [SO₄²⁻] and [SCN⁻]. Means ± relative standard error (RSE) from 9 cells. continuous lines show data from cells expressing only YFP as negative control (n = 5). C, plot of SO₄²⁻ -induced current amplitude reduction at +200 mV versus non-linear capacitance measured under the same ionic conditions for 9 different cells. In these experiments, transiently transfected HEK293T cells were used. Cells expressing YFP were accumulated into a single bin at Q_max= 0 fC and the current amplitude is shown as the mean ± standard deviation. E, current–voltage relationships from cells stably expressing Slc26a5 (DANRE)/prestin in solutions with varying [SO₄²⁻] and [SCN⁻]. Means ± SEM from 7 cells. F, dose–response relationship for sulphate block of SCN⁻ currents mediated by Slc26a5 (DANRE)/prestin. Means ± SEM (n = 7). Currents were recorded at +200 mV membrane potential and then normalized to the current amplitude at [SO₄²⁻]= 75 mm.