Abstract
Folates have been shown to be neurotoxic and convulsive. Endogenously, folates exist in the brain in a polyglutamated form with 1-7 terminal glutamates (approx. 1 microM). The brain enzyme N-acetylated alpha-linked acidic dipeptidase (NAALADase) has been shown to remove sequentially the gamma-linked glutamates from folic acid polyglutamates. We report that, at high concentrations (300 microM-30 mM), a folic acid hexaglutamate analog is dose-dependently toxic to dissociated rat cortical cultures and that this toxicity is reversed by 2-PMPA, a potent and selective NAALADase inhibitor. These data suggest a new mechanism for folic acid toxicity.
MeSH terms
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6-Cyano-7-nitroquinoxaline-2,3-dione / pharmacology
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Animals
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Benzoates / pharmacology
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Carboxypeptidases / antagonists & inhibitors*
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Cells, Cultured
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Cerebral Cortex / cytology
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Cerebral Cortex / physiology
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Deoxyglucose / pharmacology
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Dizocilpine Maleate / pharmacology
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Dose-Response Relationship, Drug
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Enzyme Inhibitors / pharmacology*
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Excitatory Amino Acid Antagonists / pharmacology
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Fetus
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Glutamate Carboxypeptidase II
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Glycine / analogs & derivatives
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Glycine / pharmacology
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Methotrexate / analogs & derivatives*
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Methotrexate / antagonists & inhibitors
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Methotrexate / toxicity
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N-Methylaspartate / pharmacology
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Neurons / cytology
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Neurons / drug effects*
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Neurons / physiology
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Neurotoxins / toxicity*
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Organophosphorus Compounds / pharmacology*
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Potassium Cyanide / pharmacology
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Pyrrolidines / pharmacology
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Rats
Substances
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2-(phosphonomethyl)pentanedioic acid
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4-amino-10-methylpteroylhexa-gamma-glutamic acid
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Benzoates
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Enzyme Inhibitors
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Excitatory Amino Acid Antagonists
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Neurotoxins
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Organophosphorus Compounds
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Pyrrolidines
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alpha-methyl-4-carboxyphenylglycine
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N-Methylaspartate
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Dizocilpine Maleate
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6-Cyano-7-nitroquinoxaline-2,3-dione
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pyrrolidin-3-yl-methanesulfonic acid
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Deoxyglucose
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Carboxypeptidases
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Glutamate Carboxypeptidase II
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Potassium Cyanide
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Glycine
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Methotrexate