Effects of monensin on amylase release from mouse parotid acini

Isolated mouse parotid acinar cells (acini) were prepared by enzyme digestion, divalent cation depletion, and mechanical shearing. Acini were found to be morphologically intact, i.e., 95% viable as judged by trypan blue exclusion. Amylase release by the cholinergic agonist carbachol, by the beta-adrenergic agonist isoproterenol, and by monensin was similar to responses obtained in mouse parotid fragments. Monensin-stimulated amylase release was associated with enhanced 22Na+ uptake and 45Ca2+ efflux; monensin did not affect 45Ca2+ uptake. In the absence of extracellular Na+, the response to monensin (50 microM) was reduced from 162 +/- 33.5 to 12.4 +/- 0.5%; monensin also failed to stimulate 45Ca2+ efflux. Similar results were obtained with isoproterenol (10(-6) M). The results suggest that Na+ ions may play a role in amylase release possibly by releasing Ca2+ from internal stores.