FIGURE 2.

Human γENaC is not sufficient for pH regulation of channel activity. A, representative traces of current versus time recorded at −60 mV from Xenopus oocytes expressing human αβγENaC (black, scale bar = 1 μA, 5 s), rat αβγENaC (light gray, scale bar = 1.3 μA, 5 s), or rat αβ- human γENaC (gray, scale bar = 1.3 μA, 6.25 s). Traces are scaled to pH 7.4 amiloride-sensitive current. Currents were recorded under conditions of high Na⁺ (116 mm) and low extracellular Cl⁻ (5 mm) over a range of pH from 9.0 to 5.25 (only pH 5.25 is shown). ENaC-dependent inward Na⁺ current was determined by application of amiloride at the end of the experiment. B, dose-response relationship showing the change in ENaC activity versus extracellular pH relative to pH 7.4 for cells expressing combinations of human and rat ENaC subunits (mean ± S.E., error bars are hidden by data symbols, human αβγENaC, black, n = 6; human γ- rat αβENaC, dark gray, n = 6, rat αβγENaC, light gray, n = 6).