Fig. 5

Na⁺-dependent H⁺ extrusion across the apical membrane of bronchiole epithelial cells. a–e Isolated bronchioles were first bilaterally perfused with the standard Hepes-buffered HCO₃⁻–CO₂-free solution (a, b) or the standard HCO₃⁻-buffered solution (c–e). Luminal Na⁺ was removed by replacement with NMDG and restored to the lumen in the absence (a, c) or presence of luminal amiloride (100 μM) (b, d) or combination of luminal amiloride (100 μM) and H₂DIDS (200 μM) (e). Time course changes of pH_i are shown as means ± SD of 8 experiments. f The activity of luminal Na⁺-dependent H⁺ extrusion is shown as the initial increase/decrease of pH_i (ΔpH for 1 min) upon restoration of luminal Na⁺. *p < 0.01, **p < 0.05