ATP-induced, sustained calcium signalling in cultured rat cortical astrocytes: evidence for a non-capacitative, P2X7-like-mediated calcium entry.
The receptor mechanisms regulating the ATP-induced free cytosolic Ca(2+) concentration ([Ca(2+)](i)) changes in cultured rat cortical type-1 astrocytes were analyzed using fura-2-based Ca(2+) imaging microscopy. Upon prolonged ATP challenge (1-100 microM), astroglial cells displayed a biphasic [Ca(2+)](i) response consisting of an initial peak followed by a sustained elevation. Suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid blocked both components, albeit to a different extent. By contrast, the selective P2X7 antagonist oxidized ATP irreversibly abrogated the sustained [Ca(2+)](i) signal without affecting the transient phase. Finally, astrocyte challenge with the selective P2X7 agonist 3'-O-(4-benzoyl)benzoyl-ATP evoked a sustained [Ca(2+)](i) elevation, which occluded that induced by ATP. We can conclude that in cultured cortical astrocytes the ATP-mediated sustained [Ca(2+)](i) rise does not implicate capacitative Ca(2+) entry but involves Ca(2+) influx through P2X7-like receptors.
Nobile
Mario
M
Institute of Biophysics, CNR, Via De Marini, 6, 16149 Genoa, Italy. nobile@icb.ge.cnr.it
Monaldi
Ilaria
I
Alloisio
Susanna
S
Cugnoli
Carlo
C
Ferroni
Stefano
S
D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D020013:Calcium Signaling; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D058486:Receptors, Purinergic P2X7; D013498:Suramin / Q000494:pharmacology
C546470:P2rx7 protein, rat; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D013498:Suramin; D000255:Adenosine Triphosphate