Effects of calcium manipulation and glucose stimulation on a histochemically detectable mobile calcium fraction in isolated rat pancreatic islets

✍ Scribed by Gerrit H. J. Wolters; A. Pasma; W. Konijnendijk; P. R. Bouman

• Publisher: Springer
• Year: 1980
• Tongue: English
• Weight: 682 KB
• Volume: 66
• Category: Article
• ISSN: 1432-119X
• DOI: 10.1007/bf00494640

✦ Synopsis

Pancreatic B-cell calcium as histochemically detectable with glyoxal bis (2-hydroxyanil)=GBHA was studied in isolated islets of fed rats. GBHA has previously been shown by us to detect an ionized or readily ionizable Ca-fraction (GBHA-Ca). In the presence of Ca + + (2.5 raM), high glucose (15 raM) induced a rapid decrease (30%) of islet GBHA-Ca followed by a rise between 30 and 60 rain to levels above the initial value. At low glucose (0 or 2.5 mM) GBHA-Ca showed a slight and gradual decline under these conditions. Omission of Ca + + at low glucose rapidly decreased (30%) islet GBHA-Ca. This decrease was markedly inhibited by high glucose, although glucose did not induce insulin secretion under these conditions. Preincubation in the absence of Ca ++ (15 rain) depleted islet GBHA-Ca, but partial restoration occurred during subsequent incubation with Ca + + at low glucose. By contrast, high glucose completely restored GBHA-Ca within 5 rain, followed by a decline and a subsequent rise. Reintroduction of Ca + + also rapidly restored the glucose-induced insulin secretion. These results indicate that islet GBHA-Ca represents a mobile Ca-fraction which is dependent on extracellular Ca ++ and which responds very rapidly to glucose stimulation. It is suggested that changes of GBHA-Ca in the B-cells may reflect changes in the Ca pool involved in the insulin secretory mechanism.