Contamination of commercially available quisqualic acid by glutamate-like and aspartate-like substances.
Six different batches of the glutamic acid analogue quisqualic acid were analyzed with high-pressure liquid chromatography (HPLC). All batches examined showed contaminant peaks. Different batches had different contaminant peaks and differing amounts of each contaminant. Every batch of quisqualic acid tested demonstrated a contaminant peak which co-eluted with exogenously added glutamic acid. Certain batches possessed a contaminant which co-eluted with aspartic acid. The levels of glutamate-like contamination ranged from 0.08 to 0.60%, and the levels of aspartate-like contamination ranged from undetectable amounts to 0.80%. The amount of combined glutamate- and aspartate-like contamination of each batch of quisqualate correlated very highly with the ability of that batch to interact with non-quisqualate receptors in an autoradiographic binding assay. These non-quisqualate receptors are likely N-methyl-D-aspartate (NMDA) receptors. Thus, when high concentrations of quisqualate are used experimentally, contamination is likely to produce spurious effects at non-quisqualate glutamate receptors. Quisqualate itself may be a more specific agonist than assumed previously.
Cha
J H
JH
Department of Neurology, University of Michigan Medical School, Ann Arbor 48104-1687.
Hollingsworth
Z R
ZR
Greenamyre
J T
JT
Young
A B
AB
D001224:Aspartic Acid / Q000032:analysis*; D002851:Chromatography, High Pressure Liquid; D004340:Drug Contamination; D005971:Glutamates / Q000032:analysis*; D018698:Glutamic Acid; D010069:Oxadiazoles / Q000032:analysis*; D016318:Quisqualic Acid
D005971:Glutamates; D010069:Oxadiazoles; D001224:Aspartic Acid; D018698:Glutamic Acid; D016318:Quisqualic Acid