L-GLUTAMATE AND GAMMA-AMINOBUTYRIC-ACID UPTAKE IN SYNAPTOSOMES FROM THE CEREBRAL-CORTEX OF DOGS WITH CONGENITAL CHRONIC HEPATIC-ENCEPHALOPATHY

High affinity [H-3]gamma-aminobutyric acid (GABA) and [H-3]L-glutamate uptake were determined in synaptosomes prepared from the cerebral cor tex of dogs with congenital hepatic encephalopathy and control dogs. T he K-m value for GABA uptake was increased by 35% but there was a conc omitant 34% increase in V-max suggesting that GABA uptake capacity was not changed in HE dogs. In contrast, mean V-max for glutamate uptake in HE dogs was 85% greater than mean V-max in control dogs; mean K-m w as increased by 25% in HE dogs. Therefore, overall synaptosomal high a ffinity glutamate uptake capacity was increased in HE dogs compared to controls.