Control of Na+ transport in salivary duct epithelial cells by cytosolic Cl- and Na+.
The duct cells of the mandibular glands of mice (and many other mammalian salivary glands) absorb NaCl from an isotonic, Na+-rich primary saliva, formed by the gland's secretory endpieces, utilising an amiloride-sensitive Na+ channel in the apical (luminal) domain of the plasma membranes. The present study focuses on the mechanisms whereby the apical membrane Na+ conductance is controlled so that the rate of Na+ influx from lumen to cytosol via the Na+ channels is matched to the rate of Na+ extrusion from cytosol to interstitium via the basolateral Na+-K+-ATPase (so called homocellular regulation or epithelial cross-talk). Our results show that the apical membrane Na+ conductance is not controlled by a sensor of extracellular (luminal) Na+, as has been previously believed, but by sensors of cytosolic Na+ and Cl- which down-regulate the Na+ channels when the cytosolic concentration of either ion increases. These effects of cytosolic Na+ and Cl- are mediated, respectively, by G proteins of the Gi and Go subclasses.
Cook
D I
DI
Dept. Physiology, University of Sydney, NSW, Australia. davidc@physiol.usyd.edu.au
Dinudom
A
A
Komwatana
P
P
Young
J A
JA
D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002712:Chlorides / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism; D051379:Mice; D018987:Salivary Ducts / Q000166:cytology / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D013363:Submandibular Gland / Q000166:cytology / Q000378:metabolism*
D002712:Chlorides; D012964:Sodium