Control of K+ conductance by cholecystokinin and Ca2+ in single pancreatic acinar cells studied by the patch-clamp technique.

The effect of cholecystokinin (CCK) and internal Ca2+ on outward K+ current in isolated pig pancreatic acinar cells has been investigated using the patch-clamp method for whole-cell current recording under voltage-clamp conditions. CCK (2 X 10(-10) M) applied to the bath evoked a marked increase in the outward K+ current associated with depolarizing voltage steps, and this effect was fully reversible and acutely dependent on the presence of external Ca2+. When strongly buffered Ca2+-EGTA solutions were used inside the cells CCK failed to evoke an effect. Increasing the internal Ca2+ concentration [( Ca2+]i) from 5 X 10(-8) M to 10(-7) and 5 X 10(-7) M mimicked the effect of CCK. It would appear therefore that CCK controls K+ conductance in the acinar cells via changes in the internal free ionized Ca2+ concentration.