A, representative whole-cell currents evoked by repeated voltage steps from −10 to −30 mV for wild-type (WT), hetKir6.2-W68R/SUR1 (hetW68R) and Kir6.2-W68R/SUR1 (homW68R) channels. The bars indicate the duration of application of 3 mm azide (black) and 0.5 mm tolbutamide (grey). The dotted line indicates the zero current level. B, mean steady-state whole-cell currents evoked by a voltage step from −10 to −30 mV before (control, black bars), and after application of 3 mm azide (white bars), and in the presence of 3 mm azide plus 0.5 mm tolbutamide (grey bars) for wild-type (WT, n = 5), and heterozygous (n = 8) and homomeric (n = 10) Kir6.2-W68R/SUR1 channels, as indicated. **P < 0.01.