Diadenosine polyphosphates (ApnAs) are released from and act on P2-subtype purinoceptors in neural cells. Using single cell fura-2 fluorescence to measure levels of free cytosolic Ca2+ ([Ca2+]j) we determined the extent to which ApnAs activate purinoceptors and increase [Ca2+]j in human fetal cultured astrocytes. Diadenosine triphosphate, diadenosine tetraphosphate and diadenosine pentaphosphate significantly increased [Ca2+]j. Diadenosine pentaphosphate (Ap5A) pressure injected (100 μM) onto astrocytes increased [Ca2+]; in 39 out of 65 astrocytes tested; peak increases ranged from 500 to 2000 nM (mean ±SEM, 820 ±142 nM). Chelation of extracellular Ca2+ with 2 mM EGTA completely blocked ApnA-induced increases in [Ca2+];. Pyridoxal-phosphate-6-azophenel-2',4'disulphonic acid tetrasodium (PPADS, 300 μM), a nonselective P2X/P2Y purinoceptor antagonist blocked, by over 50 %, Ap5A-induced increases in [Ca2+]j. Thapsigargin (4 μM), a Ca2+ ATPase inhibitor that depletes Ca2+ stores, blocked, by over 75%, ApsA-induced increases in [Ca2+]j. Activation of purinoceptor subtypes by ApnAs results in significant increases in [Ca2+]j and a significant component of the [Ca2+]; is released from intracellular stores in human fetal astrocytes.
|Original language||English (US)|
|Publication status||Published - Dec 1 1996|
ASJC Scopus subject areas
- Molecular Biology