A fluorimetric and amperometric study of calcium and secretion in isolated mouse pancreatic beta-cells.
We have examined the temporal relationship between intracellular Ca2+ concentration ([Ca2+]i) and secretion in single intact pancreatic beta-cells. Secretion was detected as the release of 5-hydroxytryptamine from pre-loaded beta-cells, using amperometry, and changes in [Ca2+]i were monitored by microfluorimetry. Stimulation of beta-cells by elevation of the extracellular K+ concentration ([K+]o), acetylcholine or glucose increased [Ca2+]i and, after a delay of 2-7 s, evoked amperometric currents. In the presence of glucose, we observed oscillations in [Ca2+]i which were associated with oscillations in the amplitude and frequency of amperometric currents: however, the temporal correlation was not exact, suggesting that there is a significant latency between the increase in average [Ca2+]i and exocytosis. Both the amplitude and frequency of the amperometric currents elicited by 50 mM KCl declined with successive stimulation, but were restored by agents which elevate intracellular adenosine 3':5':cyclic monophosphate (cAMP). This suggests that beta-cells may possess a readily releasable pool of granules which is replenished by cAMP. The variable amplitude of the amperometric currents is discussed in terms of a model in which several secretory granules fuse simultaneously with the plasma membrane.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D004563:Electrochemistry; D004594:Electrophysiology; D005089:Exocytosis; D005470:Fluorometry; D005947:Glucose / Q000494:pharmacology; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008839:Microelectrodes; D011189:Potassium Chloride / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism
D005576:Colforsin; D012701:Serotonin; D011189:Potassium Chloride; D005947:Glucose; D000109:Acetylcholine; D002118:Calcium