Fig. 1

Luminal microperfusion of an isolated bronchiole and measurement of intracellular pH. a, b The proximal end of an isolated bronchiole (inner diameter: ~ 150 μm) is held and cannulated for luminal microperfusion (20–30 μl/min). The representative bronchiole is bifurcated. The luminal perfusate leaving the distal end of the bronchiole is diluted and washed away by the flow (~ 3 ml/min) of solution through the bath. c Fluorescence of BCECF in surface epithelial cells lining the bronchiole. Small regions of the surface epithelium are selected (such as a rectangle) and the intracellular pH (pH_i) is estimated by microfluorometry at 37 °C. d Isolated bronchioles were bilaterally perfused with the standard HCO₃⁻-buffered solution and NH₄Cl (20 mM) was applied to the lumen. Time course changes of pH_i are shown as means ± SD of 5 experiments