Mathematical modelling of stimulus-secretion coupling in the pancreatic B-cell. IV. Dissociated time course for the glucose-induced changes in distinct Ca2+ movements.

A mathematical model for the interaction between Ca and cyclic AMP in the process of glucose-stimulated insulin release from the pancreatic B-cell is presented. This model, which takes into account such features as the stratification of cytosolic Ca and the process of Ca-stimulated Ca release from the vacuolar system, entails a dissociated time course for the effect of glucose upon distinct Ca movements. Thus, whereas glucose is postulated to cause a rapid and sustained facilitation of Ca pumping into intracellular organelles, the glucose-induced stimulation of Ca influx into the B-cell is assumed to represent a delayed and discontinuous phenomenon. Such a dissociated time course allows for a fair simulation of both 45Ca efflux and insulin release from islets perifused in the absence or presence of Ca and exposed to a sudden increase in extracellular glucose concentration.