Published online Apr 21, 2006. doi: 10.3748/wjg.v12.i15.2406
Revised: November 2, 2005
Accepted: November 18, 2005
Published online: April 21, 2006
AIM: To assess whether portacaval anastomosis (PCA) in rats affects the protein expression and/or activity of glutaminase in kidneys, intestines and in three brain areas of cortex, basal ganglia and cerebellum and to explain the neurological alterations found in hepatic encephalopathy (HE).
METHODS: Sixteen male Wistar rats weighing 250-350 g were grouped into sham-operation control (n = 8) or portacaval shunt (n = 8). Twenty-eight days after the procedure, the animals were sacrificed. The duodenum, kidney and brain were removed, homogenised and mitochondria were isolated. Ammonia was measured in brain and blood. Phosphate-activated glutaminase (PAG) activity was determined by measuring ammonia production following incubation for one hour at 37 °C with O-phthalaldehyde (OPA) and specific activity expressed in units per gram of protein (µkat/g of protein). Protein expression was measured by immunoblotting.
RESULTS: Duodenal and kidney PAG activities together with protein content were significantly higher in PCA group than in control or sham-operated rats (duodenum PAG activity was 976.95±268.87 µkat/g of protein in PCA rats vs 429.19±126.92 µkat/g of protein in sham-operated rats; kidneys PAG activity was 1259.18 ± 228.79 µkat/g protein in PCA rats vs 669.67± 400.8 µkat/g of protein in controls, P < 0.05; duodenal protein content: 173% in PCA vs sham-operated rats; in kidneys the content of protein was 152% in PCA vs sham-operated rats). PAG activity and protein expression in PCA rats were higher in cortex and basal ganglia than those in sham-operated rats (cortex: 6646.6 ± 1870.4 µkat/g of protein vs 3573.8 ± 2037.4 µkat/g of protein in control rats, P < 0.01; basal ganglia, PAG activity was 3657.3 ± 1469.6 μkat/g of protein in PCA rats vs 2271.2 ± 384 μkat/g of protein in sham operated rats, P < 0.05; In the cerebellum, the PAG activity was 2471.6 ± 701.4 μkat/g of protein vs 1452.9 ± 567.8 μkat/g of protein in the PCA and sham rats, respectively, P < 0.05; content of protein: cerebral cortex: 162% ± 40% vs 100% ± 26%, P < 0.009; and basal ganglia: 140% ± 39% vs 100% ± 14%, P < 0.05; but not in cerebellum: 100% ± 25% vs 100% ± 16%, P = ns).
CONCLUSION: Increased PAG activity in kidney and duodenum could contribute significantly to the hyperammonaemia in PCA rats, animal model of encephalopathy. PAG is increased in non-synaptic mitochondria from the cortex and basal ganglia and could be implicated in the pathogenesis of hepatic encephalopathy. Therefore, PAG could be a possible target for the treatment of HE or liver dysfunction.