Abstract
High affinity [3H]γ-aminobutyric acid (GABA) and [3H]L-glutamate uptake were determined in synaptosomes prepared from the cerebral cortex of dogs with congenital hepatic encephalopathy and control dogs. The Km value for GABA uptake was increased by 35% but there was a concomitant 34% increase in Vmax suggesting that GABA uptake capacity was not changed in HE dogs. In contrast, mean Vmax for glutamate uptake in HE dogs was 85% greater than mean Vmax in control dogs; mean Km was increased by 25% in HE dogs. Therefore, overall synaptosomal high affinity glutamate uptake capacity was increased in HE dogs compared to controls.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Butterworth R. F. (1992). Pathogenesis and treatment of portal-systemic encephalopathy: an update.Dig. Dis. Sci. 3:321–327.
Debler E. A. and Lajtha A. (1987). High affinity transport of γ-aminobutyric acid, glycine, taurine, L-aspartic acid, and L-glutamic acid in synaptosomal (P2) tissue: A kinetic and substrate specificity analysis.J. Neurochem. 48:1851–1856.
Dodd P. R., Watson W. E. J., Morrison M. M., Johnston G. A. R., Bird E. D., Cowburn R. F. and Hardy J. A. (1989). Uptake of γ-aminobutyric acid and L-glutamic acid by synaptosomes from postmortem human cerebral cortex: multiple sites, sodium dependence and effect of tissue preparation.Brain Res. 490:320–331
Fonnum F. (1984). Glutamate: A neurotransmitter in mammalian brain.J. Neurochem. 42:1–11
Lowry C. H., Rosebrough S. M., Farr A. L. and Randall R. J. (1951). Protein measurement with folin-phenol reagent.J. Biol. Chem. 193:265–275.
Maddison J. E. (1988). Canine congenital portosystemic encephalopathy.Aust. Vet. J. 65:245–249.
Munson P. J. and Rodbard D. (1980). LIGAND; A versatile computerized approach for characterisation of ligand binding systems.Anal. Biochem. 107:220–239.
Norenberg M. D. (1990). Astrocytes in hepatic encephalopathy.Adv. Exp. Med. Biol. 272:81–97
Norenberg M. D., Mozes L. W., Papendick R. E. and Norenberg L. (1985). Effect of ammonia on glutamate, γ-aminobutyric acid and rubidium uptake by astrocytes.Anal. Neurol. 18:149.
Rao V. L. R. and Murthy Ch. R. K. (1991). Hyperammonaemic alterations in the uptake and release of glutamate and aspartate by rat cerebellar preparations.Neurosci. Lett. 130:49–52.
Schmidt W., Wolf G., Grüngreiff K., Meier M. and Reum T. (1990). Hepatic encephalopathy influences high-affinity uptake of transmitter glutamate and aspartate into hippocampal formation.Metab. Brain Dis. 5:19–31.
Schmidt W., Wolf G., Grüngreiff K. and Linke K. (1993). Adenosine influences the high affinity uptake of transmitter glutamate and aspartate under conditions of hepatic encephalopathy.Metab. Brain Dis. 8:73–80.
Walpole R. E. (1982).Introduction to Statistics, McMillan, New York.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Maddison, J.E., Watson, W.E.J. & Johnston, G.A.R. L-glutamate and γ-aminobutyric acid uptake in synaptosomes from the cerebral cortex of dogs with congenital chronic hepatic encephalopathy. Metab Brain Dis 10, 135–141 (1995). https://doi.org/10.1007/BF01991861
Received:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF01991861