Characterization of single potassium channels in mouse pancreatic acinar cells

1. Single K(+)-selective channels with a conductance of about 48 pS (pipette, 145 mM KCl; bath, 140 mM NaCl + 4.7 mM KCl) were recorded in the patch-clamp whole-cell configuration in isolated mouse pancreatic acinar cells. 2. Neither application of the secretagogues acetylcholine (second messenger, inositol 1,4,5-trisphosphate) or secretin (second messenger, cAMP), nor addition of the catalytic subunit of protein kinase A to the pipette solution changed the activity of the 48 pS K+ channel. 3. Intracellular acidification with sodium propionate (20 mM) diminished activity of the 48 pS channel, whereas channel open probability was increased by cytosolic alkalization with 20 mM NH4Cl. 4. BaCl2 (5 mM), TEA (10 mM) or apamin (1 microM) added to the bath solution had no obvious effect on the kinetics of the 48 pS channel. Similarly, glibenclamide and diazoxide failed to influence the channel activity. 5. When extracellular NaCl was replaced by KCl, whole-cell recordings revealed an inwardly rectifying K+ current carried by a 17 pS K+ channel. 6. The inwardly rectifying K+ current was not pH dependent and could largely be blocked by Ba2+ but not by TEA. 7. Since the 48 pS K+ channel is neither Ca2+ nor cAMP regulated, we suggest that this channel could play a role in the maintenance of the negative cell resting potential.