Figure 2. Forskolin‐stimulated transepithelial anion secretion is reduced in conditions of acute hypercapnia in Calu‐3 cells .

Calu‐3 cells were grown on permeable Snapwell supports and 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⁻] was reduced to 40 mm and cells were stimulated with forskolin (Fsk; 5 μm) before addition of apical CFTR_inh‐172 (20 μm) and basolateral bumetanide (Bumet; 25 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 < 0.01). Data represent mean ± SEM; n = 10 for normocapnia and n = 8 for hypercapnia.