Glutamine synthetase activity and glutamate uptake in hippocampus and frontal cortex in portal hypertensive rats.
OBJECTIVE
To study glutamine synthetase (GS) activity and glutamate uptake in the hippocampus and frontal cortex (FC) from rats with prehepatic portal vein hypertension.


METHODS
Male Wistar rats were divided into sham-operated group and a portal hypertension (PH) group with a regulated stricture of the portal vein. Animals were sacrificed by decapitation 14 d after portal vein stricture. GS activity was determined in the hippocampus and FC. Specific uptake of radiolabeled L-glutamate was studied using synaptosome-enriched fractions that were freshly prepared from both brain areas.


RESULTS
We observed that the activity of GS increased in the hippocampus of PH rats, as compared to control animals, and decreased in the FC. A significant decrease in glutamate uptake was found in both brain areas, and was more marked in the hippocampus. The decrease in glutamate uptake might have been caused by a deficient transport function, significantly and persistent increase in this excitatory neurotransmitter activity.


CONCLUSIONS
The presence of moderate ammonia blood levels may add to the toxicity of excitotoxic glutamate in the brain, which causes alterations in brain function. Portal vein stricture that causes portal hypertension modifies the normal function in some brain regions.
Acosta
Gabriela Beatriz
GB
Institute of Pharmacological Research (ININFA), National Research Council of Argentina (CONICET) and University of Buenos Aires, , Buenos Aires, Argentina. gacosta@ffyb.uba.ar
Fernández
María Alejandra
MA
Roselló
Diego Martín
DM
Tomaro
María Luján
ML
Balestrasse
Karina
K
Lemberg
Abraham
A
D000641:Ammonia / Q000097:blood; D000818:Animals; D005625:Frontal Lobe / Q000378:metabolism*; D005974:Glutamate-Ammonia Ligase / Q000378:metabolism*; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism*; D006624:Hippocampus / Q000378:metabolism*; D006801:Humans; D006975:Hypertension, Portal / Q000378:metabolism* / Q000503:physiopathology; D008297:Male; D051381:Rats; D017208:Rats, Wistar; D014316:Tritium / Q000378:metabolism
D014316:Tritium; D018698:Glutamic Acid; D000641:Ammonia; D005974:Glutamate-Ammonia Ligase