The gamma-subunit of Na-K-ATPase is incorporated into plasma membranes of mouse IMCD3 cells in response to hypertonicity

Am J Physiol Renal Physiol. 2005 Apr;288(4):F650-7. doi: 10.1152/ajprenal.00162.2004. Epub 2004 Nov 30.


Hypertonicity mediated by chloride upregulates the expression of the gamma-subunit of Na-K-ATPase in cultured cells derived from the murine inner medullary collecting duct (IMCD3; Capasso JM, Rivard CJ, Enomoto LM, and Berl T. Proc Natl Acad Sci USA 100: 6428-6433, 2003). The purpose of this study was to examine the cellular locations and the time course of gamma-subunit expression after long-term adaptation and acute hypertonic challenges induced with different salts. Cells were analyzed by confocal immunofluorescence and immunoelectron microscopy with antibodies against the COOH terminus of the Na-K-ATPase gamma-subunit or the gamma(b) splice variant. Cells grown in 300 mosmol/kgH(2)O showed no immunoreactivity for the gamma-subunit, whereas cells adapted to 600 or 900 mosmol/kgH(2)O demonstrated distinct reactivity located at the plasma membrane of all cells. IMCD3 cell cultures acutely challenged to 550 mosmol/kgH(2)O with sodium chloride or choline chloride showed incorporation of gamma into plasma membrane 12 h after osmotic challenge and distinct membrane staining in approximately 40% of the cells 48 h after osmotic shock. In contrast, challenging the IMCD3 cells to 550 mosmol/kgH(2)O by addition of sodium acetate did not result in expression of the gamma-subunit in the membranes of surviving cells after 48 h. The present results demonstrate that the Na-K-ATPase gamma-subunit becomes incorporated into the basolateral membrane of IMCD3 cells after both acute hyperosmotic challenge and hyperosmotic adaptation. We conclude that the gamma-subunit has an important role in the function of Na-K-ATPase to sustain the cellular cation balance over the plasma membrane in a hypertonic environment.

Publication types

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

MeSH terms

  • Adaptation, Physiological
  • Animals
  • Blotting, Western
  • Cell Membrane / metabolism*
  • Cell Polarity
  • Cells, Cultured
  • Hypertonic Solutions
  • Immunohistochemistry
  • Kidney Medulla / cytology
  • Kidney Medulla / enzymology*
  • Mice
  • Osmotic Pressure
  • Sodium-Potassium-Exchanging ATPase / metabolism*
  • Water-Electrolyte Balance / physiology*


  • Hypertonic Solutions
  • Fxyd2 protein, mouse
  • Sodium-Potassium-Exchanging ATPase