ENaC protein expression along the distal nephron. (A) Center: A bright field image of an isolated fragment from mouse kidney together with the designation of anatomically defined segments. The image was divided into five regions (S1–S5) for confocal fluorescent imaging showing ENaC (green), NCC (red), and DAPI nuclear (purple) signals. Little ENaC is expressed in S1, the region with the highest NCC signal. ENaC is seen mostly at the apical pole in regions S2 and S3. In S4 and S5, ENaC is distributed broadly within the cytoplasm. Scale bars, 10 μm. (B) Quantitation of ENaC and NCC abundance. For each region, signals were normalized to the total intensity along the entire segment. Mean tubule diameter along the tubules (blue) was also measured. P values indicate significance of differences from S5 (red) or from S1 (blue, green). Data represent mean ± SEM for seven tubules from seven different animals.