Osmotic regulation of intestinal epithelial Na(+)-K(+)-Cl- cotransport: role of Cl- and F-actin

Am J Physiol. 1998 Mar;274(3):C697-706. doi: 10.1152/ajpcell.1998.274.3.C697.


Previous data indicate that adenosine 3',5'-cyclic monophosphate activates the epithelial basolateral Na(+)-K(+)-Cl- cotransporter in microfilament-dependent fashion in part by direct action but also in response to apical Cl- loss (due to cell shrinkage or decreased intracellular Cl-). To further address the actin dependence of Na(+)-K(+)-Cl- cotransport, human epithelial T84 monolayers were exposed to anisotonicity, and isotopic flux analysis was performed. Na(+)-K(+)-Cl- cotransport was activated by hypertonicity induced by added mannitol but not added NaCl. Cotransport was also markedly activated by hypotonic stress, a response that appeared to be due in part to reduction of extracellular Cl- concentration and also to activation of K+ and Cl- efflux pathways. Stabilization of actin with phalloidin blunted cotransporter activation by hypotonicity and abolished hypotonic activation of K+ and Cl- efflux. However, phalloidin did not prevent activation of cotransport by hypertonicity or isosmotic reduction of extracellular Cl-. Conversely, hypertonic but not hypotonic activation was attenuated by the microfilament disassembler cytochalasin D. The results emphasize the complex interrelationship among intracellular Cl- activity, cell volume, and the actin cytoskeleton in the regulation of epithelial Cl- transport.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism*
  • Carrier Proteins / metabolism*
  • Cells, Cultured
  • Chlorides / metabolism*
  • Cytochalasin D / metabolism
  • Cytoskeleton / metabolism
  • Humans
  • Intestinal Mucosa / metabolism*
  • Membrane Proteins / metabolism*
  • Microscopy, Fluorescence
  • Phalloidine / pharmacology
  • Potassium / metabolism*
  • Rubidium / pharmacology
  • Sodium / metabolism*
  • Sodium-Potassium-Chloride Symporters
  • Water-Electrolyte Balance*


  • Actins
  • Carrier Proteins
  • Chlorides
  • Membrane Proteins
  • Sodium-Potassium-Chloride Symporters
  • Phalloidine
  • Cytochalasin D
  • Sodium
  • Rubidium
  • Potassium