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<b>THE INTERACTION BETWEEN BARIUM AND CALCIUM IN β-CELL-RICH PANCREATIC </b><b>ISLETS </b>

1983; Allied Academies; Volume: 4; Issue: 2 Linguagem: Inglês

10.2220/biomedres.4.129

1880-313X

Per‐Olof Berggren, Tommy Andersson, Bo Hellman,

Curcumin's Biomedical Applications

The interactions between Ba" and Ca" were examined in ,8-cell-rich pancreatic islets isolated from non-inbred ob/ob mice.Measurements with electrothermal atomic absorption spectroscopy enabled the demonstration of transport of Ba" into the cells and subsequent incorporation of the element into organelles such as mitochondria and secretory granules.An increase of the glucose concentration from 1 to 20 mM stimulated the barium uptake into the secretory granules without significantly affecting the contents of barium in other organelles or the islet homogenate.The islet uptake of Ba" was suppressed in the presence of Mg" or Ca", the concentration dependence of the Ca" effect being compatible with an inhibitory action also on the intracellular buffering of Ba".Whereas low concentrations of Ba" (0.05-2.5 mM) stimulated the incorporation of "Ca, there was no increase of the accumulation beyond the uptake obtained when the ,6-cells were depolarized with high concentrations of glucose (20 mM) or IQ" (30.9 mM).The exposure to Ba" resulted in transient mobilization of the "Ca incorporated in response to glucose both in the presence and absence of Ca".When introduced into a Ca"-deficient medium, 2.5 mM Ba" was clearly stimulatory also when Na+ or K+ were omitted or the Mg" concentration was increased to 12 mM.It seems likely from the relationships observed between Ba" and Ca" fluxes, that exposure to Ba" increases the cytoplasmic concentration of Ca" even in a Ca"-deficient medium.The insulin-releasing action of Ba" may consequently be an indirect effect mediated by Ca".