CYTOSOLIC CA2-CELLS STIMULATED BY GLUCOSE AND CARBACHOL( GRADIENTS INPANCREATIC ISLET)

Digital image analysis was employed to resolve the spatial differences in distribution of cytosolic free Ca2+ concentrations ([Ca2+](i)) in mouse pancreatic islet-cells stimulated with glucose and carbachol, Us ing Indo-1 loaded mouse islet-cells, we have demonstrated that glucose induces steep spatial gradients of [Ca2+](i) in isolated mouse islet- cells, Furthermore, the largest [Ca2+](i) increase was always spatiall y restricted to a region just beneath the plasma membrane, Low concent rations 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 [Ca2+](i) to high levels collapsing the [Ca2+](i) gradients in the center of the cells, Different patterns of [Ca2+](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 oscil late with the same pattern as the whole islet, We postulate that ''ini tiators'' of insulin release, as glucose, induce greater [Ca2+](i) inc reases at exocytotic sites than those induced by ''potentiators'', as carbachol, (C) 1997 Academic Press.