Uridine activates fast transmembrane Ca2+ ion fluxes in rat brain homogenates

Kardos, Julianna and Kovács, Ilona and Szárics, Éva and Kovács, Richárd and Skuban, N. and Nyitrai, Gabriella and Dobolyi, Árpád and Juhász, Gábor Dénes (1999) Uridine activates fast transmembrane Ca2+ ion fluxes in rat brain homogenates. NEUROREPORT, 10 (7). pp. 1577-1582. ISSN 0959-4965

Text 1232060.pdf Restricted to Repository staff only Download (518kB) | Request a copy

Abstract

Excitatory receptors responsive to extracellular pyrimidine nucleotides have been identi®ed [1±6]. Although there is evidence for uridine acting as a CNS depressant [7,8], suggestions for an excitatory role in the CNS have so far not been supported by any direct evidence at the molecular level [9]. Hepatic uridine [10] enters the extracellular space of the brain, and subsequently brain cells, from the blood, where it can be phosphorylated and incorporated into RNA or be catabolized to uracil [11,12]. Since the extracellular concentration of uridine has been found to be increased by high K+ in the rat thalamus [13], it was of interest to study uridineresponsive cation ¯uxes through brain membranes. Here we describe a ¯uorescent tracer method to study uridine-activated Ca2+ and K+ ion translocation in suspensions of resealed plasmalemma fragments and nerve endings on the time scale achievable by stopped-¯ow spectroscopy. Uptake, release and binding of radiolabeled uridine in suspensions of synaptosomes and synaptosomal membranes, respectively, were also measured. Cerebral ±cortical suspensions were controlled by HPLC analyses of endogenous purines and pyrimidines.

Actions (login required)

Edit Item