A fluorimetric and amperometric study of calcium and secretion in isolated mouse pancreatic beta-cells
Smith, P.A.; Duchen, M.R.; Ashcroft, F.M.
Pflugers Archiv European Journal of Physiology 430(5): 808-818
1995
ISSN/ISBN: 0031-6768 PMID: 7478937 Document Number: 440346
We have examined the temporal relationship between intracellular Ca-2+ concentration ((Ca-2+)-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 (Ca-2+)-i were monitored by microfluorimetry. Stimulation of beta-cells by elevation of the extracellular K+ concentration ((K+)-o), acetylcholine or glucose increased (Ca-2+)-i and, after a delay of 2-7 s, evoked amperometric currents. In the presence of glucose, we observed oscillations in (Ca-2+)-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 (Ca-2+)-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.