ISOPROTERENOL EVOKES EXTRACELLULAR CA2-GLAND CELLS (VOL 273, PG 4106,1998)( SPIKES DUE TO SECRETORY EVENTS IN SALIVARY)

Citation
P. Belan et al., ISOPROTERENOL EVOKES EXTRACELLULAR CA2-GLAND CELLS (VOL 273, PG 4106,1998)( SPIKES DUE TO SECRETORY EVENTS IN SALIVARY), The Journal of biological chemistry, 273(17), 1998, pp. 10806
Citations number
40
Categorie Soggetti
Biology
ISSN journal
00219258
Volume
273
Issue
17
Year of publication
1998
Database
ISI
SICI code
0021-9258(1998)273:17<10806:IEECC(>2.0.ZU;2-1
Abstract
Secretory cells should in principle export substantial amounts of calc ium via exocytosis since Ca2+ is sequestered in secretory granules. Ba sed on a new technique for measurements of the extracellular calcium c oncentration in the vicinity of the cell membrane and on the droplet t echnique, we have monitored the rate of calcium extrusion from salivar y gland acinar cells. Isoproterenol (ISP), a beta-adrenergic agonist a nd powerful secretogogue, evoked no change in the cytosolic free Ca2concentration ([Ca2+](i)) but induced vigorous extracellular Ca2+ conc entration ([Ca2+](o)) spiking. The absence of [Ca2+](i) elevation and the pulsatile nature of the changes in [Ca2+](o) indicate that these s pikes are most likely due to calcium release from secretory granules. The cholinergic agonist acetylcholine (ACh), which induces moderate se cretion, evoked a marked rise in [Ca2+](i) and a smooth rise in [Ca2+] (o), most likely induced by plasma membrane calcium pumps, on which sh ortlasting [Ca2+](o) spikes were superimposed. The rate of ISP-induced calcium efflux was very substantial. The calculated calcium loss duri ng the first 100 s of supramaximal stimulation corresponded to a reduc tion of the total cellular calcium concentration of approximately 0.4 mm. We conclude that in salivary glands, calcium release via exocytosi s is one of the main mechanisms extruding calcium from cells to the ex tracellular milieu.