Inhibition of glutamate uptake causes an acute increase in aqueous humor protein

Exp Eye Res. 1997 Feb;64(2):157-65. doi: 10.1006/exer.1996.0180.


Inhibition of glutamate transport has been shown to increase paracellular permeability of epithelial cell monolayers in vitro. To determine if blocking glutamate transport would affect tissue permeability in vivo, D-aspartate (D-Asp; 300 nmol 30 microliters-1) (a non-toxic competitive inhibitor of glutamate transport) or a placebo was injected into the anterior chambers of the fellow eyes of 15 adult rabbits. [14C]-L-glucose and/or [125I]-rabbit albumin were included in the injection vehicle as aqueous humor (AH) outflow markers. The specific inhibition of glutamate uptake by D-Asp was indicated by a 15% increase in AH glutamate (174 +/- 9 nmol ml-1 to 205 +/- 13 nmol ml-1; P = 0.03) at 1-1.5 hr post injection. Also, the efflux of [14C]-L-glucose and [125I]-rabbit albumin from the AH of D-Asp injected eyes was increased 22% over the placebo-injected control eyes (P < or = 0.02). Concomitantly, the total protein concentration in the AH from D-Asp injected eyes (517 +/- 35 micrograms ml-1) was 19% greater (P < 0.02) than the protein concentration in AH from placebo-injected control eyes (420 +/- 36 micrograms ml-1). In additional studies, an irreversible inhibitor of glutamate transport, threo-beta-hydroxyaspartate (THA; 30 nmol 30 microliters-1), was shown to increase the efflux of [14C]-L-glucose (22%; P < 0.05) from the anterior chamber and increase AH protein concentrations by 29% (484 +/- 112 micrograms ml-1 in control AH versus 686 +/- 117 micrograms ml-1 in THA AH, P = 0.08) at 1 hr post intracameral injection. SDS-PAGE analysis of the AH associated the protein increase in the D-Asp and THA injected eyes but not placebo-injected control eyes with a detectable increase in a 66 kDa protein (aligns with serum albumin) and several lower molecular weight (23-35 kDa) AH proteins. The results found suggest that inhibition of glutamate transport from the AH acutely increases intraocular epithelial/endothelial paracellular permeability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alanine / metabolism
  • Animals
  • Aqueous Humor / drug effects*
  • Aqueous Humor / metabolism
  • Aspartic Acid / analogs & derivatives
  • Aspartic Acid / metabolism
  • Aspartic Acid / pharmacology
  • Biological Transport / drug effects
  • Cell Membrane Permeability / drug effects
  • Excitatory Amino Acid Antagonists / pharmacology*
  • Eye Proteins / analysis
  • Eye Proteins / metabolism*
  • Female
  • Glutamic Acid / metabolism*
  • Glutamine / metabolism
  • Male
  • Rabbits


  • Excitatory Amino Acid Antagonists
  • Eye Proteins
  • Glutamine
  • 3-hydroxyaspartic acid
  • Aspartic Acid
  • Glutamic Acid
  • Alanine