Glutamine synthetase activity and glutamate uptake in hippocampus and frontal cortex in portal hypertensive rats

Abstract

AIM: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 shamoperated 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. CONCLUSION: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.

Exposure to As, Cd and Pb-mixture impairs myelin and axon development in rat brain, optic nerve and retina

“…Precipitated proteins were removed by centrifugation at 10,000 g, and the absorbance of the supernatants was read at 535 nm against a reagent blank. GS specific activity was expressed as μmol γ-glutamylhydroxamate per hour per milligram of protein (Acosta et al, 2009).…”

Age and High-Fat Diet Effects on Glutamine Synthetase Immunoreactivity in Liver and Hippocampus and Recognition Memory in Mice

“…Acosta et al . [29] found the GS enzyme activity to be increased in the hippocampus but decreased in the frontal cortex of male Wistar rats with surgically induced portal hypertension and hyperammonemia.…”

Gut-Brain Chemokine Changes in Portal Hypertensive Rats

“…In particular, a growing body of evidence points towards a key role of the hippocampus in prehepatic portal hypertensive encephalopathy [43,44]. The hippocampus plays important roles in cognitive processes, most notably learning and memory, and is selectively vulnerable to ischemic insults.…”