Figure 4.

[Na⁺] in ASL of mouse distal airways. The ASL was stained with 200-nm diameter polystyrene beads containing Na⁺-sensitive Corona red^TM (red fluorescing) and Na⁺-insensitive BODIPY-fl (green fluorescing). (A) Ratio of red-to-green fluorescence (R/G) of the Na⁺ indicator as a function of [Na⁺] in PBS in which Na⁺ was replaced by choline⁺ (open circles). Also shown in averaged R/G and deduced [Na⁺] in ASL of distal airways (filled circle). (B) Green (left) and red (middle) images of fluorescently-stained distal airways. Spatial map of ASL [Na⁺] shown as pseudocolored ratio image (right). Bar, 100 μm. (C). ASL [Na⁺] measured in airways of indicated size (left) and after indicated maneuvers (right). Maneuvers include ENaC and CFTR inhibition, and pulmonary artery perfusion with 0 Na⁺ buffer for 45 min before measurements (“Na⁺ free”).