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 × 10^-10M) 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 × 10^-10M to 10^-7 and 5 × 10^-7M 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.