Previous studies have shown that Ca2+ -induced enzyme secretion in pancreatic acinar cells involves activation of ion conductances in ZG membranes (F. Thévenod 2002 Am J Physiol 283:C651). In ZG suspensions ion flux was determined by ionophore-induced osmotic lysis of ZG suspended in isotonic salts. The KCNQ1 inhibitor 293B blocked K+ conductance only (IC50 ~10 mM). Fusion of ZG membranes with planar bilayer membranes identified K+ channels in 645/150 mM K-gluconate (cis/trans). Channels had linear current-voltage relationships and reversal potential of -20.3 ± 1.3 mV (n = 33). K+ channels with conductances of 1.5 ± 0.2 nS (n = 6) and 139.2 ± 3.7 pS (n = 3) were inhibitable by 100 mM 293B or the more specific inhibitor HMR 1556. Immunoblotting and immunogold labelling reveales KCNQ1 expression in ZG membranes. 293B blocked cholecystokinin-induced amylase secretion from permeabilised pancreatic acini (IC50 ~10 mM), when coincubated with flufenamate, which inhibits ZG non-selective cation conductance. KCNQ1 may account for ZG K+ conductance and contribute to hormone-stimulated secretion of pancreatic digestive enzymes. Funded by Mukoviszidose e.V. FT 04/04