Figure 8. The αW493R mutation abolishes Na⁺ self inhibition.

Oocytes were injected with 0.5 ng per subunit of cRNA for αβγENaC (wt) or α_W493RβγENaC (αW493R). After 2 days of incubation in low Na⁺, oocytes were clamped at −100 mV. The bath solution initially contained 1 mm Na⁺ and was subsequently changed to a bath solution containing 110 mm Na⁺ as indicated. After 60 s, amiloride (2 μm) was applied to determine the ENaC-mediated current component. A, representative current traces of a wild-type (left) and a mutant ENaC (right)-expressing oocyte. Downward deflections represent inward currents. B, averaged current traces from similar experiments as shown in A, starting from the change to 110 mm Na⁺. Lines represent mean, error bars s.e.m. n indicate number of oocytes.