Summary

Calu-3 cells secrete HCO3- in response to cAMP agonists but can be stimulated to secrete Cl- with K+ channel activating agonists. Microelectrode and impedance analysis experiments were performed to obtain a better understanding of the conductances and driving forces involved in these different modes of anion secretion in Calu-3 cells. Microelectrode studies revealed apical and basolateral membrane depolarizations upon the addition of forskolin (Vap –52 mV vs. –21 mV; Vbl –60 mV vs. –44 mV) that paralleled the hyperpolarization of the mucosal negative transepithelial voltage (VT –8 mV vs. –23 mV). These changes were accompanied by a decrease in the apical membrane fractional resistance (FRap) from approximately 0.50 to 0.08, consistent with the activation of an apical membrane conductance. The subsequent addition of 1-ethyl-2-benzimidazolinone (1-EBIO), a K+ channel activator, hyperpolarized Vap to – 27 mV, Vbl to – 60 mV and VT to – 3