PORTACAVAL ANASTOMOSIS RESULTS IN ALTERED NEURON-ASTROCYTIC METABOLICTRAFFICKING OF AMINO-ACIDS - EVIDENCE FROM C-13-NMR STUDIES

C-13-NMR spectroscopy was used to evaluate the dynamic consequences of portacaval anastomosis on neuronal and astrocytic metabolism and meta bolic trafficking between neurons and astrocytes. Glutamate is predomi nantly labeled from [1-C-13]glucose, whereas [2-C-13]acetate is more e fficient in labeling glutamine, in accordance with its primary metabol ism in astrocytes. Alanine and succinate labeling was only observed wi th [1-C-13]glucose as precursor. Brain [1-C-13]glucose metabolism in p ortacaval-shunted rats was similar to that in sham-operated controls w ith the exception of labeled glutamine and succinate formation, which was increased in shunted rats. The C-13 enrichment was, however, decre ased owing to an increase in total glutamine and succinate. Using [2-C -13]acetate, on the other hand, flux of astrocytic label to neurons wa s severely decreased because label incorporation into glutamate, aspar tate, and GABA was decreased following portacaval shunting. The latter amino acids are predominantly localized in neurons. These findings de monstrate that metabolic trafficking of amino acids from astrocytes to neurons is impaired in portacaval-shunted rats.