Extracellular potassium regulates the glutamine content of astrocytes: mediation by intracellular pH

Neurosci Lett. 1993 Sep 17;160(1):73-6. doi: 10.1016/0304-3940(93)9002-7.


Based upon previous evidence that glutamine formation in astrocytes is pH-sensitive and that raised extracellular K+ alkalinizes astrocytic cytoplasm, it was hypothesized that extracellular K+ might regulate glutamine formation. In this study, the free glutamine content of mouse cerebral astrocytes incubated with 0.1 mM glutamate and 0.1 mM ammonium increased by 80-90% when the extracellular K+ concentration was raised from 3 to 12 mM. The corresponding K(+)-induced intracellular alkalinization of +0.13 pH units only partially reversed a glutamate-induced intracellular acidification of -0.24 pH units. By comparison, adjustment of extracellular pH from 7.4 to 7.8 shifted intracellular pH by +0.25 pH units, fully reversing the glutamate-induced acidification and increasing glutamine content by 120-180%. The effect of K+ on intracellular pH increased to +0.25 pH units in bicarbonate-buffered solution, suggesting that the regulation of glutamine formation by extracellular K+ is enhanced in the presence of bicarbonate.

Publication types

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

MeSH terms

  • Ammonia / metabolism
  • Animals
  • Astrocytes / drug effects
  • Astrocytes / metabolism*
  • Bicarbonates / pharmacology
  • Cell Membrane Permeability / drug effects
  • Cells, Cultured
  • Glutamine / metabolism*
  • Hydrogen-Ion Concentration
  • Mice
  • Potassium / physiology*
  • Spectrometry, Fluorescence


  • Bicarbonates
  • Glutamine
  • Ammonia
  • Potassium