ATP stimulates calcium-dependent glutamate release from cultured astrocytes.
ATP caused a dose-dependent, receptor-mediated increase in the release of glutamate and aspartate from cultured astrocytes. Using calcium imaging in combination HPLC we found that the increase in intracellular calcium coincided with an increase in glutamate and aspartate release. Competitive antagonists of P(2) receptors blocked the response to ATP. The increase in intracellular calcium and release of glutamate evoked by ATP were not abolished in low Ca(2+)-EGTA saline, suggesting the involvement of intracellular calcium stores. Pre-treatment of glial cultures with an intracellular Ca(2+) chelator abolished the stimulatory effects of ATP. Thapsigargin (1 microM), an inhibitor of Ca(2+)-ATPase from the Ca(2+) pump of internal stores, significantly reduced the calcium transients and the release of aspartate and glutamate evoked by ATP. U73122 (10 microM, a phospholipase C inhibitor, attenuated the ATP-stimulatory effect on calcium transients and blocked ATP-evoked glutamate release in astrocytes. Replacement of extracellular sodium with choline failed to influence ATP-induced glutamate release. Furthermore, inhibition of the glutamate transporters p-chloromercuri-phenylsulfonic acid and Ltrans-pyrolidine-2,4-dicarboxylate failed to impair the ability of ATP to stimulate glutamate release from astrocytes. However, an anion transport inhibitor, furosemide, and a potent Cl(-) channel blocker, 5-nitro-2(3-phenylpropylamino)-benzoate, reduced ATP-induced glutamate release. These results suggest that ATP stimulates excitatory amino acid release from astrocytes via a calcium-dependent anion-transport sensitive mechanism.
Jeremic
A
A
Department of Biomedical Sciences, Neuroscience Program, Iowa State University, Ames, USA.
Jeftinija
K
K
Stevanovic
J
J
Glavaski
A
A
Jeftinija
S
S
D002731:4-Chloromercuribenzenesulfonate / Q000494:pharmacology; D018528:ATP-Binding Cassette Transporters / Q000037:antagonists & inhibitors; D000255:Adenosine Triphosphate / Q000494:pharmacology*; D027322:Amino Acid Transport System X-AG; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001253:Astrocytes / Q000187:drug effects* / Q000378:metabolism; D002110:Caffeine / Q000494:pharmacology; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002478:Cells, Cultured / Q000187:drug effects / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology; D002614:Chelating Agents / Q000494:pharmacology; D018118:Chloride Channels / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D004533:Egtazic Acid / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D005665:Furosemide / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism*; D017136:Ion Transport / Q000187:drug effects; D009579:Nitrobenzoates / Q000494:pharmacology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D012433:Ryanodine / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D019284:Thapsigargin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D002614:Chelating Agents; D018118:Chloride Channels; D004791:Enzyme Inhibitors; D004963:Estrenes; D009579:Nitrobenzoates; D011760:Pyrrolidinones; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D012433:Ryanodine; D001224:Aspartic Acid; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D002110:Caffeine; D018698:Glutamic Acid; D004533:Egtazic Acid; D002731:4-Chloromercuribenzenesulfonate; D019284:Thapsigargin; D005665:Furosemide; D000255:Adenosine Triphosphate; D012964:Sodium; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D000252:Calcium-Transporting ATPases