Mechanisms of Ca2+-stimulated fluid secretion by porcine bronchial submucosal gland serous acinar cells.
The serous acini of airway submucosal glands are important for fluid secretion in the lung. Serous cells are also sites of expression of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channel. However, the mechanisms of serous cell fluid secretion remain poorly defined. In this study, serous acinar cells were isolated from porcine bronchi and studied using optical techniques previously used to examine fluid secretion in rat parotid and murine nasal acinar cells. When stimulated with the cholinergic agonist carbachol, porcine serous cells shrank by approximately 20% (observed via DIC microscopy) after a profound elevation of intracellular [Ca(2+)] ([Ca(2+)](i); measured by simultaneous fura 2 fluorescence imaging). Upon removal of agonist and relaxation of [Ca(2+)](i) to resting levels, cells swelled back to resting volume. Similar results were observed during stimulation with histamine and ATP, and elevation of [Ca(2+)](i) was found to be necessary and sufficient to activate shrinkage. Cell volume changes were associated with changes in [Cl(-)](i) (measured using SPQ fluorescence), suggesting that shrinkage and swelling are caused by loss and gain of intracellular solute content, respectively, likely reflecting changes in the secretory state of the cells. Shrinkage was inhibited by niflumic acid but not by GlyH-101, suggesting Ca(2+)-activated secretion is mediated by alternative non-CFTR Cl(-) channels, possibly including Ano1 (TMEM16A), expressed on the apical membrane of porcine serous cells. Optimal cell swelling/solute uptake required activity of the Na(+)K(+)2Cl(-) cotransporter and Na(+)/H(+) exchanger, both of which are expressed on the basolateral membrane of serous acini and likely contribute to sustaining transepithelial secretion.
Lee
Robert J
RJ
Departments of Physiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Foskett
J Kevin
JK
D000818:Animals; D000075369:Anoctamin-1; D001826:Body Fluids / Q000378:metabolism*; D001980:Bronchi / Q000166:cytology* / Q000378:metabolism; D002034:Bumetanide / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002217:Carbachol / Q000378:metabolism; D048429:Cell Size; D002478:Cells, Cultured; D018118:Chloride Channels / Q000378:metabolism; D002712:Chlorides / Q000378:metabolism; D018679:Cholinergic Agonists / Q000378:metabolism; D019005:Cystic Fibrosis Transmembrane Conductance Regulator / Q000037:antagonists & inhibitors / Q000378:metabolism; D005088:Exocrine Glands / Q000378:metabolism*; D020869:Gene Expression Profiling; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009544:Niflumic Acid / Q000378:metabolism; D051381:Rats; D049994:Sodium Potassium Chloride Symporter Inhibitors / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism; D064506:Solute Carrier Family 12, Member 2; D013552:Swine
C531181:ANO1 protein, mouse; D000075369:Anoctamin-1; D018118:Chloride Channels; D002712:Chlorides; D018679:Cholinergic Agonists; C578877:SLC12A2 protein, human; C578878:Slc12a2 protein, mouse; C578879:Slc12a2 protein, rat; D049994:Sodium Potassium Chloride Symporter Inhibitors; D017923:Sodium-Hydrogen Exchangers; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D002034:Bumetanide; D019005:Cystic Fibrosis Transmembrane Conductance Regulator; D009544:Niflumic Acid; D002217:Carbachol; D002118:Calcium