1379631

Alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid binding to human cerebral cortical membranes: minimal changes in postmortem brains of chronic schizophrenics.

Article date: 1992/9/1

PubMed ID: 1379631

Journal name: Journal of neurochemistry (ISSN: 0022-3042)

ABSTRACT

The binding of alpha-[3H]amino-3-hydroxy-5-methylisoxazole-4-propionic acid ([3H]AMPA), a selective ligand for the ion channel-linked quisqualate receptor, was evaluated in Triton X-100-treated membranes of human cerebral cortex. The presence of chaotropic ions produced divergent effects on specific [3H]AMPA binding: A twofold increase in the binding was observed with thiocyanide at 100 mM, although iodide (100 mM) and perchlorate (100 mM) reduced the binding. Chemical modifications of the sulfhydryl group with p-chloromercuriphenylsulfonic acid (PCMBS) produced threefold increases in specific [3H]-AMPA binding in the absence of KSCN as well as in the presence of KSCN. Treatment with dithiothreitol restored the enhanced specific [3H]AMPA binding by PCMBS to the basal level. Although specific [3H]AMPA binding in the absence of KSCN showed a single site (KD = 220 nM, Bmax = 235 fmol/mg of protein), curvilinear Scatchard plots of specific [3H]AMPA binding in the presence of 100 mM KSCN can be resolved into two binding sites with the following parameters: KD1 = 5.82 nM, Bmax1 = 247 fmol/mg of protein; KD2 = 214 nM, Bmax2 = 424 fmol/mg of protein. Quisqualate and AMPA were the most potent inhibitors of the [3H]AMPA binding in the presence of KSCN. Potent inhibitors of the binding included beta-N-oxalylamino-L-alanine (L-BOAA), cysteine-S-sulfate, L-glutamate, 6-cyano-7-nitroquinoxaline-2,3-dione, and 6,7-dinitroquinoxaline-2,3-dione. Kainate, L-homocysteine sulfinic acid, and L-homocysteic acid were active with an IC50 value of a micromolar concentration, whereas L-cysteic acid and L-cysteine sulfinic acid were weakly active.(ABSTRACT TRUNCATED AT 250 WORDS)

Author List: Kurumaji A, Ishimaru M, Toru M

Publication Types: Journal Article; Research Support, Non-U.S. Gov't

Substances mentioned in the article: Tritium; Ibotenic Acid; 4-Chloromercuribenzenesulfonate; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid;

Mesh terms: 4-Chloromercuribenzenesulfonate/pharmacology; Adult; Aged; Brain/metabolism; Cerebral Cortex/metabolism; Chronic Disease; Female; Humans; Ibotenic Acid/analogs & derivatives; Male; Membranes/metabolism; Middle Aged; Reference Values; Schizophrenia/metabolism; Tissue Distribution; Tritium; alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid;

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