Cytoplasmic Ca2+ signals evoked by activation of cholecystokinin receptors: Ca(2+)-dependent current recording in internally perfused pancreatic acinar cells.
The effects on the cytosolic Ca2+ concentration of activating cholecystokinin receptors on single mouse pancreatic acinar cells have been investigated using patch-clamp whole-cell recording of Ca(2+)-dependent Cl- current. We used the nonsulphated octapeptide of cholecystokinin (CCK8-NS) since the effects of even high concentrations were rapidly reversible which was not the case for the sulphated octapeptide. A submaximal concentration of CCK8-NS (10 nM) evoked a current response consisting of short-lasting (a few seconds) spikes, and some of these spikes were seen to trigger larger and longer (about half a minute) current pulses. At a higher concentration (100 nM) CCK8-NS evoked smooth and sustained responses. The effect of CCK8-NS was almost abolished when the internal perfusion solution contained a high concentration of the Ca2+ chelator EGTA (5 mM). The responses evoked by CCK8-NS were independent of the presence of Ca2+ in the external solution at least for the first 5 min of stimulation. Internal perfusion with GTP-gamma-S markedly potentiated the effect of CCK8-NS or at a higher concentration itself induced responses very similar to those normally evoked by CCK8-NS. Caffeine added to the external solution at a low concentration (0.2-1 mM) enhanced weak CCK8-NS responses, whereas high caffeine concentrations always inhibited the CCK8-NS-evoked responses. These inhibitory caffeine effects were quickly reversible. Forskolin evoked a similar inhibitory effect. Intracellular heparin (200 micrograms/ml) infusion markedly inhibited the response to CCK8-NS stimulation. We conclude that the primary effect of activating CCK receptors is to induce inositoltrisphosphate (IP3) production.(ABSTRACT TRUNCATED AT 250 WORDS)
Wakui
M
M
Physiological Laboratory, University of Liverpool, United Kingdom.
Kase
H
H
Petersen
O H
OH
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000378:metabolism*; D002766:Cholecystokinin / Q000378:metabolism / Q000494:pharmacology*; D003593:Cytoplasm / Q000378:metabolism; D004347:Drug Interactions; D004553:Electric Conductivity; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006493:Heparin / Q000494:pharmacology; D066298:In Vitro Techniques; D051379:Mice; D010179:Pancreas / Q000166:cytology / Q000378:metabolism* / Q000502:physiology; D010477:Perfusion; D011949:Receptors, Cholecystokinin / Q000378:metabolism*; D015398:Signal Transduction; D013431:Sulfates / Q000494:pharmacology
D015220:Calcium Channels; D011949:Receptors, Cholecystokinin; D013431:Sulfates; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D002110:Caffeine; D006493:Heparin; D002766:Cholecystokinin; D002118:Calcium