Ammonia stimulates the release of taurine from cultured astrocytes

The effect of ammonia on the release of the neuroactive amino acids taurine (TAU), gamma-aminobutyric acid (GABA) and D-aspartate (D-ASP), an analog of L-glutamate (L-GLU), from cultured rat cortical astrocytes was studied. NH4Cl (1 and 5 mM) induced the release of TAU. TAU release was reduced when Na+ was removed, and was almost completely abolished when Cl- was omitted. In contrast, TAU basal release was enhanced upon removal of Na+ or Cl-. Ammonia inhibited the release of GABA and D-ASP. Ammonia-induced release of astroglial TAU may modify the neuronal excitability accompanying hyperammonemic conditions.