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Activation of purinergic P2X receptors inhibits P2Y-mediated Ca2+ influx in human microglia.

Authors
Wang, X; Kim, SU; van Breemen, C; McLarnon, JG
Citation
Cell calcium, 27(4):205-212, 2000
Journal Title
Cell calcium
ISSN
0143-41601532-1991
Abstract
Purinoceptor (P2X and P2Y) mediated Ca2+ signaling in cultured human microglia was studied using Ca2+ sensitive fluorescence microscopy. ATP (at 100 microM) induced a transient increase in [Ca2+]i in both normal and Ca(2+)-free solution suggesting a primary contribution by release from intracellular stores. This conclusion was further supported by the failure of ATP to cause a divalent cationic influx in Mn2+ quenching experiments. However, when fluorescence quenching was repeated after removal of extracellular Na+, ATP induced a large influx of Mn2+, indicating that inward Na+ current through a non-selective P2X-coupled channel may normally suppress divalent cation influx. Inhibition of Mn2+ entry was also found when microglia were depolarized using elevated external K+ in Na(+)-free solutions. The possibility of P2X inhibition of Ca2+ influx was then investigated by minimizing P2X contributions of purinergic responses using either the specific P2Y agonist, ADP-beta-S in the absence of ATP or using ATP combined with PPADS, a specific inhibitor of P2X receptors. In quenching studies both procedures resulted in large increases in Mn2+ influx in contrast to the lack of effect observed with ATP. In addition, perfusion of either ATP plus PPADS or ADP-beta-S alone caused a significantly enhanced duration (about 200%) of the [Ca2+]i response relative to that induced by ATP. These results show that depolarization induced by P2X-mediated Na+ influx inhibits store-operated Ca2+ entry resulting from P2Y activation, thereby modulating purinergic signaling in human microglia.
MeSH terms
Adenosine Diphosphate/analogs & derivatives/pharmacologyAdenosine Triphosphate/pharmacologyCalcium/*metabolismCalcium SignalingCulture MediaFluorescenceHumansIon Channels/drug effects/metabolismManganese/metabolismMicroglia/drug effects/*metabolismPurinergic P2 Receptor AntagonistsPyridoxal Phosphate/analogs & derivatives/pharmacologyReceptors, Purinergic P2/drug effects/*metabolismThionucleotides/pharmacology
PMID
10858666
Appears in Collections:
Journal Papers > School of Medicine / Graduate School of Medicine > Neurology
AJOU Authors
김, 승업
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