Figure 9. Forskolin‐stimulated transepithelial anion secretion is reduced in conditions of acute hypercapnia in primary human bronchial epithelial cells .

Primary human bronchial epithelial cells were grown on collagen‐coated permeable Snapwell supports and allowed to differentiate at an ALI for 30–35 days before I _sc was measured using an Ussing chamber. A, a representative I _sc recording of a control experiment in which cells were exposed to 5% (v/v) CO₂/95% (v/v) O₂; B, a representative recording in which cells were pre‐exposed to 10% (v/v) CO₂/90% (v/v) O₂ for 20 min prior to being studied. Apical [Cl⁻] and basolateral [Cl⁻] were both 124 mm for these experiments. Cells were treated with apical amiloride (Amil; 10 μm) and stimulated with forskolin (Fsk; 10 μm) before addition of apical CFTR_inh‐172 (20 μm) as indicated. C–F, basal I _sc (C), maximal forskolin‐stimulated increase in I _sc (D), rate of increase in forskolin‐stimulated I _sc (E) and amount of forskolin‐stimulated current that was inhibitied by CFTR_inh‐172 (F). *Significant effect of hypercapnia (P < 0.05). Data represent mean ± SEM; n = 6 for each.