Glutamic Acid Decarboxylase and γ‐Aminobutyric Acid in Huntington's Disease Fibroblasts and Other Cultured Cells, Determined by a [3H]Muscimol Radioreceptor Assay

Abstract

A sensitive and reproducible [3H]muscimol radioreceptor assay was developed for measuring low levels of both glutamic acid decarboxylase activity and GABA. By using this technique, endogenous GABA and glutamic acid decarboxylase activity were detected in 2 rat neuroblastomas, B35 and B50, a human medulloblastoma cell line, TE671, and cultured human skin fibroblasts. Glutamic acid decarboxylase activity and GABA levels were compared for human skin fibroblasts obtained from patients with Huntington''s disease and their controls in a well-controlled, blind study. No significant difference was found for either measure between Huntington and control cells. Glutamic acid decarboxylase activity was relatively low in all cell types examined except for the TE671 cells, which had more than 4 times the activity found in the other cells. This human medulloblastoma cell line appears to be a good model for studying GABA metabolism and the control of glutamic acid decarboxylase expression.