Characteristics of chloride-dependent incorporation of glutamate into brain membranes argue against a receptor binding site

R. Zaczek, Stephanie Arlis, Andrea Markl, T. Murphy, Harriet Drucker, J. T. Coyle

Research output: Contribution to journalArticlepeer-review

Abstract

Although membrane sites from brain, labelled with [3H]glutamate (Glu) under sodium-free conditions, are thought to represent excitatory receptors, certain anomalous characteristics of the kinetics of apparent binding raised the question of whether transport might contribute to this process, prompting a closer examination of it. Hyperosmolar media and low incubation temperatures (4°C) both led to decreases in the apparent specific binding of [3H]glutamate to membranes from the brain of the rat in the presence of chloride. Furthermore, only 15% of the [3H]glutamate, bound at 37°C, was dissociable when the membranes were then cooled to 4°C. The binding of [3H]glutamate was increased in the presence of certain dipeptides such as l-phenylalanyl-l-glutamate (Phe-Glu); and the binding augmented by the presence of Phe-Glu, was also sensitive to temperature and osmolarity of the incubation buffer. Sonication of membranes in 5mM glutamate increased the apparent binding of [3H]glutamate and abolished the stimulatory effect of Phe-Glu. These findings are consistent with the hypothesis that chloride-dependent association of [3H]glutamate with membranes from brain reflects, in part, a sequestration process, which may be driven by glutamate exchange.

Original languageEnglish (US)
Pages (from-to)281-287
Number of pages7
JournalNeuropharmacology
Volume26
Issue number4
DOIs
StatePublished - Apr 1987

Keywords

  • excitatory amino acids
  • glutamate
  • quisqualate
  • receptors
  • transport

ASJC Scopus subject areas

  • Pharmacology
  • Cellular and Molecular Neuroscience

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