SIMILARITY OF GLUTAMATE-DECARBOXYLASE AND GABA TRANSAMINASE IN TERMS OF RESPONSE TO THEIR INHIBITORS IN PANCREATIC-ISLETS IN-VITRO

To investigate the properties of the glutamate decarboxylase (GAD), a gamma-aminobutyric acid (GABA) synthesizing enzyme, and GABA transamin ase (GABA-T), a GABA degrading enzyme, in the pancreatic islets of the rats, GABA concentrations in the islets were measured in vitro after incubation with 3-mercaptopropionic acid (3-MP) or sodium-n-dipropyl-a cetate (sodium valproate). Sixty minutes after the incubation with 3-M P, GABA concentrations in the pancreatic islets decreased within the r ange 10(-7)-10(-4)M, while sixty minutes after incubation with sodium valproate, they increased within the range 10(-7)-10(-4)M with a dose dependent response. The activities of GAD and GABA-T in the pancreatic islets can be modified by a convulsant, in this case 3-MP, and by an anticonvulsant, sodium valproate. These results suggest that the prope rties of GAD and GABA-T may be similar in the pancreatic islets and br ain.