Cytosolic Ca2+ gradients in pancreatic islet-cells stimulated by glucose and carbachol
Martín, F.; Ribas, J.; Soria, B.
Biochemical and Biophysical Research Communications 235(3): 465-468
1997
ISSN/ISBN: 0006-291X PMID: 9207177 Document Number: 480664
Digital image analysis was employed to resolve the spatial differences in distribution of cytosolic free Ca-2+ concentrations ((Ca-2+)-i) in mouse pancreatic islet-cells stimulated with glucose and carbachol. Using Indo-1 loaded mouse islet-cells, we have demonstrated that glucose induces steep spatial gradients of (Ca-2+)-i in isolated mouse islet-cells. Furthermore, the largest (Ca-2+)-i increase was always spatially restricted to a region just beneath the plasma membrane. Low concentrations of carbachol (0.6 mu-M) induced steep spatial gradients of (Ca-2+)-i which originated from the center of the cells. However, 10 mu-M carbachol increased (Ca-2+)-i to high levels collapsing the (Ca-2+)-i gradients in the center of the cells. Different patterns of (Ca-2+)-i oscillations were observed between dissociated pancreatic islet-cells and mouse pancreatic islets when challenged with 11 mM glucose. Under these conditions we could identify cells within the islet which oscillate with the same pattern as the whole islet. We postulate that "initiators" of insulin release, as glucose, induce greater (Ca-2+)-i increases at exocytotic sites than those induced by "potentiators", as carbachol.