Chronic and selective inhibition of basolateral membrane Na-K-ATPase uniquely regulates brush border membrane Na absorption in intestinal epithelial cells

Am J Physiol Cell Physiol. 2015 Apr 15;308(8):C650-6. doi: 10.1152/ajpcell.00355.2014. Epub 2015 Feb 4.


Na-K-ATPase, an integral membrane protein in mammalian cells, is responsible for maintaining the favorable intracellular Na gradient necessary to promote Na-coupled solute cotransport processes [e.g., Na-glucose cotransport (SGLT1)]. Inhibition of brush border membrane (BBM) SGLT1 is, at least in part, due to the diminished Na-K-ATPase in villus cells from chronically inflamed rabbit intestine. The aim of the present study was to determine the effect of Na-K-ATPase inhibition on the two major BBM Na absorptive pathways, specifically Na-glucose cotransport and Na/H exchange (NHE), in intestinal epithelial (IEC-18) cells. Na-K-ATPase was inhibited using 1 mM ouabain or siRNA for Na-K-ATPase-α1 in IEC-18 cells. SGLT1 activity was determined as 3-O-methyl-D-[(3)H]glucose uptake. Na-K-ATPase activity was measured as the amount of inorganic phosphate released. Treatment with ouabain resulted in SGLT1 inhibition at 1 h but stimulation at 24 h. To further characterize this unexpected stimulation of SGLT1, siRNA silencing was utilized to inhibit Na-K-ATPase-α1. SGLT1 activity was significantly upregulated by Na-K-ATPase silencing, while NHE3 activity remained unaltered. Kinetics showed that the mechanism of stimulation of SGLT1 activity was secondary to an increase in affinity of the cotransporter for glucose without a change in the number of cotransporters. Molecular studies demonstrated that the mechanism of stimulation was not secondary to altered BBM SGLT1 protein levels. Chronic and direct silencing of basolateral Na-K-ATPase uniquely regulates BBM Na absorptive pathways in intestinal epithelial cells. Specifically, while BBM NHE3 is unaffected, SGLT1 is stimulated secondary to enhanced affinity of the cotransporter.

Keywords: Na-K-ATPase; Na-glucose cotransporter; SGLT1; intestinal inflammation; ouabain.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Biological Transport / genetics
  • Biological Transport / physiology
  • Cell Line
  • Coccidiosis / parasitology
  • Coccidiosis / pathology
  • Eimeria / immunology
  • Eimeria / pathogenicity
  • Enzyme Activation
  • Enzyme Inhibitors / pharmacology
  • Intestinal Absorption / drug effects
  • Intestinal Absorption / genetics
  • Intestinal Absorption / physiology*
  • Intestinal Mucosa / cytology
  • Intestinal Mucosa / enzymology
  • Intestine, Small / cytology
  • Male
  • Microvilli / metabolism*
  • Ouabain / pharmacology
  • RNA Interference
  • RNA, Small Interfering
  • Rabbits
  • Rats
  • Sodium / metabolism
  • Sodium-Glucose Transporter 1 / antagonists & inhibitors
  • Sodium-Glucose Transporter 1 / genetics
  • Sodium-Glucose Transporter 1 / metabolism*
  • Sodium-Hydrogen Exchanger 3
  • Sodium-Hydrogen Exchangers / metabolism*
  • Sodium-Potassium-Exchanging ATPase / antagonists & inhibitors
  • Sodium-Potassium-Exchanging ATPase / genetics
  • Sodium-Potassium-Exchanging ATPase / metabolism*


  • Enzyme Inhibitors
  • RNA, Small Interfering
  • Slc5a1 protein, rat
  • Slc9a3 protein, rat
  • Sodium-Glucose Transporter 1
  • Sodium-Hydrogen Exchanger 3
  • Sodium-Hydrogen Exchangers
  • Ouabain
  • Sodium
  • Sodium-Potassium-Exchanging ATPase