Effect of extracellular manganese on amylase release from dispersed pancreatic acini.

In dispersed acini from guinea pig pancreas, adding extracellular manganese increased amylase release. A significant effect could be detected with 0.25 mM manganese, and maximal stimulation occurred with 1 mM manganese. When manganese was added, the rate of amylase release did not change during the first 20 min of incubation and then gradually increased to a new steady state by 80 min, which with 1 mM manganese represented a fourfold increase in the rate of enzyme release. Extracellular manganese inhibited the stimulation of amylase release caused by those secretagogues that mobilize cellular calcium but augmented the stimulation caused by those secretagogues whose actions are mediated by cellular cAMP. The mechanism by which manganese altered stimulated amylase secretion differed from the mechanism by which manganese stimulated basal amylase release because the change in stimulated release was maximal within 10 min, whereas the change in basal release did not occur until after 20 min. The actions of manganese on secretagogue-stimulated amylase release were not attributable to manganese-induced changes in secretagogue-stimulated calcium outflux or cAMP and, instead, appear to result from actions of manganese on one of the later steps in the mechanisms for stimulating the secretory process.