Fig. 4.

Increased ENaC function in Nedd4L conditional KO lungs and isolated type II cells. (A) Decreased wet/dry ratio of lungs harvested at 4 h postpartum from Nedd4L KO (Nedd4L^f/f;SPC-rtTA;tet^o-Cre) vs. Control (Nedd4L^f/f;SPC-rtTA or Nedd4L^f/f;tet^o-Cre) mice. Values are mean ± SD of 5–7 mice. P < 0.005 (Student’s t test). (B) Whole-cell patch-clamp recording to analyze ENaC activity in alveolar-type II cells isolated from lungs of 2-wk-old Nedd4L KO mice (Nedd4L^f/f;SPC-rtTA;tet^o-Cre) and controls (Nedd4L^f/f;SPC-rtTA). (A and B) Representative traces show the currents recorded during the voltage ramp from -100 to +60 mV before (−) and after (+) adding 10 μM amiloride in a control (A) cell and a KO (B) cell. The amiloride-sensitive difference currents are illustrated. (C) A plot showing average amiloride (10 μM) -sensitive currents in control (n = 19) and KO (n = 33) cells. The gray areas are ± 1 SEM for each point. (D) Bar graph showing average amiloride-sensitive (± SEM) conductance at the concentrations of amiloride tested (0.3, 1, or 10 μM) in control (n = 12) and KO (n = 24) cells. ***p < 0.001 compared with corresponding control group. (E) A plot showing average 1-μM benzamil-sensitive currents in control (n = 20) and KO (n = 26) cells. (F) Bar graph showing average benzamil-sensitive conductance at the concentrations of benzamil tested (0.1 or 1 μM) in control (n = 15) and KO (n = 25) cells. **p < 0.01, ***p < 0.001 compared with corresponding control group (Mann–Whitney U test). For all patch-clamp experiments, type II cells were isolated from 11 KO and 14 control mice, which originated from six different litters.