Fig. 8.

The reduced sodium self-inhibition of human and guinea pig δβγ-ENaC generates increased activity at high extracellular Na⁺ concentrations. (A) Representative transmembrane current (I_M) traces of guinea pig αβγ- and δβγ-ENaC at different extracellular Na⁺ concentrations ([Na⁺]). Recordings of a given extracellular [Na⁺] were performed in individual oocytes. The perfusion speed was 16 ml/min. (B, C) The percentage of sodium self-inhibition for guinea pig and human ENaC expressing oocytes plotted against logarithmic transformations of concentrations of extracellular [Na⁺]. SSI was calculated as (ΔI_M peak−ΔI_M 3 min)/ΔI_M peak×100, where ΔI_M peak=I_M under X mM [Na⁺] peak −initial I_M under 1 mM [Na⁺], and ΔI_M 3 min=I_M after 3 min under X mM [Na⁺]−initial I_M under 1 mM [Na⁺]. Slopes (sl.) were derived from linear regressions and P values, derived from ANCOVA, demonstrate the difference between slopes. Numbers in parentheses indicate (n).