Enhanced potassium-stimulated gamma-aminobutyric acid release by astrocytes derived from rats with early hepatogenic encephalopathy.

Bulk-isolated astrocytes from rats with early hepatogenic encephalopathy (HE) induced with thioacetamide responded to the increase of potassium in the incubation medium from 5 mM to 75 mM with a markedly enhanced release of previously taken up [14C]gamma-aminobutyric acid ([14C]GABA). The process was not affected by omission of calcium and/or addition of EGTA to the incubation medium. Only a slight stimulation of GABA release by high potassium was observed in astrocytes from control rats. In contrast, histamine and histidine were vigorously released from control astrocytes in high-potassium medium, and their release was not enhanced by HE, indicating that the observed phenomenon is specific for GABA.