title: Uridine activates fast transmembrane Ca2+ ion fluxes in rat brain homogenates.
abstract: The excitatory actions of the pyrimidine nucleoside uridine, and the nucleotides UDP and UTP, as well as the purine nucleotide ATP, were studied by fluorescent labeling of Ca2+ and K+ ion fluxes on the time scale of 0.04 ms to 10s in resealed plasmalemma fragments and nerve endings from the rat cerebral cortex. Two phases of Ca2+ ion influx with onsets of a few milliseconds and a few hundred milliseconds, showing different concentration dependencies, agonist sequences and subcellular localizations were distinguishable. [3H]Uridine identified high (K(D) approximately 15 nM) and low affinity (K(D)approximately 1 microM) specific binding sites in purified synaptosomal membranes. Labeled uridine taken up by synaptosomes in a dipyridamole-sensitive process was released by depolarization (1 mM 4-aminopyridine). Taken together, these results may qualify uridine as a neurotransmitter.
authors.affiliation: Department of Neurochemistry, Chemical Institute, Chemical Research Center, Hungarian Academy of Sciences, Budapest.
authors.forename: J
authors.initials: J
authors.lastname: Kardos
authors.forename: I
authors.initials: I
authors.lastname: Kovács
authors.forename: E
authors.initials: E
authors.lastname: Szárics
authors.forename: R
authors.initials: R
authors.lastname: Kovács
authors.forename: N
authors.initials: N
authors.lastname: Skuban
authors.forename: G
authors.initials: G
authors.lastname: Nyitrai
authors.forename: A
authors.initials: A
authors.lastname: Dobolyi
authors.forename: G
authors.initials: G
authors.lastname: Juhász
mesh_terms: D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000187:drug effects* / Q000648:ultrastructure; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D008297:Male; D009411:Nerve Endings / Q000187:drug effects / Q000648:ultrastructure; D015221:Potassium Channels / Q000819:agonists; D051381:Rats; D017208:Rats, Wistar; D013050:Spectrometry, Fluorescence; D013574:Synaptosomes / Q000187:drug effects*; D014316:Tritium; D014529:Uridine / Q000494:pharmacology*
chemical_list: D002120:Calcium Channel Agonists; D005456:Fluorescent Dyes; D015221:Potassium Channels; D014316:Tritium; D014529:Uridine