Cytoplasmic Ca2+ oscillations evoked by receptor stimulation, G-protein activation, internal application of inositol trisphosphate or Ca2+: simultaneous microfluorimetry and Ca2+ dependent Cl- current recording in single pancreatic acinar cells.

The effects of acetylcholine (ACh), cholecystokinin (CCK), internally applied GTP-gamma-S, inositol trisphosphate Ins (1,4,5) P3] or Ca2+ on the cytoplasmic free Ca2+ concentration ( Ca2+]i) were assessed by simultaneous microfluorimetry (fura-2) and measurement of the Ca2(+)-dependent Cl- current (patch-clamp whole-cell recording) in single internally perfused mouse pancreatic acinar cells. ACh (0.1-0.2 microM) evoked an oscillating increase in Ca2+]i measured in the cell as a whole (microfluorimetry) which was synchronous with oscillations in the Ca2(+)-dependent Cl- current reporting Ca2+]i close to the cell membrane. In the same cells a lower ACh concentration (0.05 microM) evoked shorter repetitive Cl- current pulses that were not accompanied by similar spikes in the microfluorimetric recording. When cells did not respond to 0.1 microM ACh, caffeine (1 mM) added on top of the sustained ACh stimulus resulted in Ca2+]i oscillations seen synchronously in both types of recording. CCK (10 nM) also evoked Ca2+]i oscillations, but with much longer intervals between slightly broader Ca2+ pulses. Internal perfusion with 100 microM GTP-gamma-S evoked Ca2+]i oscillations with a similar pattern. Ins (1,4,5) P3 (10 microM) evoked repetitive shortlasting spikes in Ca2+]i that were only seen in the Cl- current traces, except in one small cell where these spikes were also observed synchronously in the microfluorimetric recording. Caffeine (1 mM) broadened these Ca2+ pulses. Ca2+]i was also directly changed, bypassing the normal signalling process, by infusion of a low or high Ca2+ solution into the pipette.(ABSTRACT TRUNCATED AT 250 WORDS)