title: Roles of basolateral solute uptake via NKCC1 and of myosin II in vasopressin-induced cell swelling in inner medullary collecting duct.
abstract: Collecting duct cells swell when exposed to arginine vasopressin (AVP) in the presence of a transepithelial osmolality gradient. We investigated the mechanisms of AVP-induced cell swelling in isolated, perfused rat inner medullary collecting ducts (IMCDs) using quantitative video microscopy and fluorescence-based measurements of transepithelial water transport. We tested the roles of transepithelial water flow, basolateral solute entry, and the cytoskeleton (actomyosin). When a transepithelial osmolality gradient was imposed by addition of NaCl to the bath, AVP significantly increased both water flux and cell height. When the osmolality gradient was imposed by addition of mannitol, AVP increased water flux but not cell height, suggesting that AVP-induced cell swelling requires a NaCl gradient and is not merely dependent on the associated water flux. Bumetanide (Na-K-2Cl cotransporter inhibitor) added to the bath markedly diminished the AVP-induced cell height increase. AVP-induced cell swelling was absent in IMCDs from NKCC1-knockout mice. In rat IMCDs, replacement of Na, K, or Cl in the peritubular bath caused significant cell shrinkage, consistent with a basolateral solute transport pathway dependent on all three ions. Immunocytochemistry using an antibody to NKCC1 confirmed basolateral expression in IMCD cells. The conventional nonmuscle myosin II inhibitor blebbistatin also diminished the AVP-induced cell height increase and cell shape change, consistent with a role for the actin cytoskeleton and myosin II. We conclude that the AVP-induced cell height increase is dependent on basolateral solute uptake via NKCC1 and changes in actin organization via myosin II, but is not dependent specifically on increased apical water entry.
authors.affiliation: National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Chung-Lin
authors.initials: CL
authors.lastname: Chou
authors.forename: Ming-Jiun
authors.initials: MJ
authors.lastname: Yu
authors.forename: Eliza M
authors.initials: EM
authors.lastname: Kassai
authors.forename: Ryan G
authors.initials: RG
authors.lastname: Morris
authors.forename: Jason D
authors.initials: JD
authors.lastname: Hoffert
authors.forename: Susan M
authors.initials: SM
authors.lastname: Wall
authors.forename: Mark A
authors.initials: MA
authors.lastname: Knepper
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology*; D002034:Bumetanide / Q000494:pharmacology; D048429:Cell Size / Q000187:drug effects; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D066298:In Vitro Techniques; D007685:Kidney Tubules, Collecting / Q000187:drug effects* / Q000502:physiology*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D024462:Myosin Type II / Q000037:antagonists & inhibitors / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D028021:Sodium-Potassium-Chloride Symporters / Q000172:deficiency / Q000502:physiology*; D064506:Solute Carrier Family 12, Member 2
chemical_list: D006576:Heterocyclic Compounds, 4 or More Rings; D012333:RNA, Messenger; C578878:Slc12a2 protein, mouse; C578879:Slc12a2 protein, rat; D028021:Sodium-Potassium-Chloride Symporters; D064506:Solute Carrier Family 12, Member 2; D002034:Bumetanide; D001127:Arginine Vasopressin; C472645:blebbistatin; D024462:Myosin Type II