Calcium dependence of exocytosis in lacrimal gland acinar cells.
Simultaneous measurements of membrane capacitance and intracellular calcium concentration were used to examine the calcium dependence of exocytosis in single acinar cells from mouse lacrimal gland and to establish the quantitative relation between calcium concentration and rate of exocytosis. Application of adrenergic or muscarinic agonists elevated intracellular calcium and evoked exocytosis, as indicated by an increase in membrane capacitance of single cells. The capacitance response to agonist stimulation was eliminated by internal dialysis with the calcium buffer EGTA, which demonstrated that the increase in intracellular calcium was necessary for agonist-evoked exocytosis. When internal calcium was elevated by application of the calcium ionophore ionomycin, exocytosis was evoked in the absence of agonist stimulation. Thus an increase in intracellular calcium was necessary and sufficient for exocytosis in single acinar cells. The rate of change of membrane capacitance increased as approximately the third power of the calcium concentration, which is similar to the dependence of exocytosis rate on calcium concentration in other secretory cells.
Sundermeier
Thomas
T
Department of Neurobiology and Behavior, State University of New York, Stony Brook, New York 11794, USA.
Matthews
Gary
G
Brink
Peter R
PR
Walcott
Benjamin
B
D000322:Adrenergic Agonists / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D018679:Cholinergic Agonists / Q000494:pharmacology; D025802:Electric Capacitance; D005089:Exocytosis / Q000502:physiology*; D007765:Lacrimal Apparatus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D009994:Osmolar Concentration
D000322:Adrenergic Agonists; D018679:Cholinergic Agonists; D002118:Calcium