Mathematical modelling of stimulus-secretion coupling in the pancreatic B-cell II. Calcium-stimulated calcium release

An attempt was made to simulate in a mathematical model one of the two major effects of glucose upon ⁴⁵Ca fractional outflow rate from prelabelled pancreatic islets, namely the increase in effluent radioactivity which is currently ascribed to the displacement of ⁴⁵Ca from intracellular sites, as resulting from a facilitated influx of unlabelled ⁴⁰Ca into the islet cells. The occurrence of such a rise in effluent radioactivity and its suppression in the absence of extracellular Ca²⁺ could only be simulated if the release of Ca by the vacuolar system was assumed to be stimulated by a rise in the cytosolic Ca concentration. It is proposed therefore that, in islets like in muscle, a process of Ca-stimulated Ca release may participate in the regulation of intracellular Ca distribution.