Activation of salivary secretion: coupling of cell volume and [Ca2+]i in single cells.
High-resolution differential interference contrast microscopy and digital imaging of the fluorescent calcium indicator dye fura-2 were performed simultaneously in single rat salivary gland acinar cells to examine the effects of muscarinic stimulation on cell volume and cytoplasmic calcium concentration ([Ca2+]i). Agonist stimulation of fluid secretion is initially associated with a rapid tenfold increase in [Ca2+]i as well as a substantial cell shrinkage. Subsequent changes of cell volume in the continued presence of agonist are tightly coupled to dynamic levels of [Ca2+]i, even during [Ca2+]i oscillations. Experiments with Ca2+ chelators and ionophores showed that physiological elevations of [Ca2+]i are necessary and sufficient to cause changes in cell volume. The relation between [Ca2+]i and cell volume suggests that the latter reflects the secretory state of the acinar cell. Agonist-induced changes in [Ca2+]i, by modulating specific ion permeabilities, result in solute movement into or out of the cell. The resultant cell volume changes may be important in modulating salivary secretion.
Foskett
J K
JK
Physiology Department, Armed Forces Radiobiology Research Institute, Bethesda, MD 20814.
Melvin
J E
JE
D000818:Animals; D001572:Benzofurans; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane / Q000502:physiology; D002614:Chelating Agents; D002712:Chlorides / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004533:Egtazic Acid / Q000031:analogs & derivatives; D004987:Ethers / Q000494:pharmacology; D005456:Fluorescent Dyes; D016257:Fura-2; D015759:Ionomycin; D007476:Ionophores; D007700:Kinetics; D011188:Potassium / Q000378:metabolism; D051381:Rats; D012463:Saliva / Q000378:metabolism*; D012469:Salivary Glands / Q000166:cytology* / Q000187:drug effects / Q000502:physiology
D001572:Benzofurans; D002614:Chelating Agents; D002712:Chlorides; D004987:Ethers; D005456:Fluorescent Dyes; D007476:Ionophores; D004533:Egtazic Acid; D015759:Ionomycin; D002217:Carbachol; C058180:5,5'-dimethyl-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetate; D011188:Potassium; D002118:Calcium; D016257:Fura-2