Amiloride-sensitive INa of triple mutant α-K561A, β-R503A, and γ-R515A channels activated by CAP2. WT α-, β-, γ-, or mutant α-K561A, β-R503A, and γ-R515A ENaC cRNA (0.3 ng each) and 1 ng CAP2 cRNA were injected into oocytes. 24 h after injection, two-electrode voltage clamp assays were conducted. Currents measured in the presence and absence of 10 μM amiloride, while clamping the membrane voltage to −100 mV, were digitized and recorded. Batches of oocytes were extracted from four different frogs (n = 24). Results are expressed as the means ± SE. Statistical significance was determined using an unpaired Student's t test. Basal WT INa versus WT trypsin-stimulated INa: *, P < 0.0001; basal WT INa versus basal triple mutant INa: **, P < 0.0011; basal triple mutant INa versus triple mutant trypsin-stimulated INa: #, significant P < 0.0001.
