CA2-MEDIATED PATHWAY DIRECTLY ACTIVATES ONLY THE K+ CURRENT BUT THE SUBSEQUENT CA2+ RELEASE FROM THE STORE ACTIVATES BOTH K+ AND CL- CURRENTS IN SUBMANDIBULAR-GLAND ACINAR-CELLS OF THE RAT( ENTRY THROUGH THE STORE)

The store-mediated Ca2+ entry was detected in single and cluster of ra t submandibular acinar cells by measuring the Ca2+ activated ionic mem brane currents. In the cells where intracellular Ca2+ was partly deple ted by stimulation with submaximal concentration of acetylcholine (ACh ) under a Ca2+-free extracellular condition, an employment of external Ca2+ in the absence of ACh caused a sustained increase of the K+ curr ent without affecting the Cl- current. A renewed ACh challenge without external Ca2+ caused repetitive spikes of both K+ and Cl- currents du e to the Ca2+ release. SK & F 96365 inhibited the generation of the su stained K+ current and refilling of the Ca2+ store following the Ca2readmission. It is suggested that the Ca2+ enters the cell through the store-mediated pathway near the K+ channels and is taken up by the st ore. Thus, only Ca2+ released from the store can activate both the Kand Cl- currents.