Fluid secretion and the Na+-K+-2Cl- cotransporter in mouse exorbital lacrimal gland.
We have previously suggested that fluid flow in the mouse exorbital lacrimal gland is driven by the opening of apical Cl- and K+ channels. These ions move into the lumen of the gland and water follows by osmosis. In many tissues, the Na+-K+-2Cl- cotransporter (NKCC1) replaces the Cl- and K+ ions that move into the lumen. We hypothesize that mouse exorbital lacrimal glands would have NKCC1 co-transporters and that they would be important in fluid transport by this gland. We used immunocytochemistry to localize NKCC1-like immunoreactivity to the membranes of the acinar cells as well as to the basolateral membranes of the duct cells. We developed a method to measure tear flow and its composition from mouse glands in situ. Stimulation with the acetylcholine agonist carbachol produced a peak flow followed by a plateau. Ion concentration measurements of this stimulated fluid showed it was high in K+ and Cl-. Treatment of the gland with furosemide, a blocker of the NKCC1 cotransporter, reduced the plateau phase of fluid flow by approximately 30%. Isolated cells exposed to a hypertonic shock shrank by approximately 20% and then showed a regulatory volume increase (RVI). Both the RVI and swelling were blocked by treatment with furosemide. Cells isolated from these glands shrink by approximately 10% in the presence of carbachol. Blocking NKCC1 with furosemide reduced the amount of shrinkage by approximately 50%. These data suggest that NKCC1 plays an important role in fluid secretion by the exorbital gland of mice.
Walcott
Benjamin
B
Centre for Visual Sciences, Research School of Biological Sciences, Australian National University, PO Box 475, Canberra ACT 2601, Australia. ben.walcott@anu.edu.au
Birzgalis
Aija
A
Moore
Leon C
LC
Brink
Peter R
PR
D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D002462:Cell Membrane; D048429:Cell Size; D004232:Diuretics / Q000494:pharmacology; D005439:Flufenamic Acid / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology; D007765:Lacrimal Apparatus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008916:Miotics / Q000494:pharmacology; D011188:Potassium / Q000502:physiology; D012964:Sodium / Q000502:physiology; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism / Q000502:physiology*; D013666:Tears / Q000378:metabolism*; D013997:Time Factors
D004232:Diuretics; D008916:Miotics; D028021:Sodium-Potassium-Chloride Symporters; D005439:Flufenamic Acid; D005665:Furosemide; D002217:Carbachol; D012964:Sodium; D011188:Potassium