Storage and release of ATP from astrocytes in culture.
ATP is released from astrocytes and is involved in the propagation of calcium waves among them. Neuronal ATP secretion is quantal and calcium-dependent, but it has been suggested that ATP release from astrocytes may not be vesicular. Here we report that, besides the described basal ATP release facilitated by exposure to calcium-free medium, astrocytes release purine under conditions of elevated calcium. The evoked release was not affected by the gap-junction blockers anandamide and flufenamic acid, thus excluding purine efflux through connexin hemichannels. Sucrose-gradient analysis revealed that a fraction of ATP is stored in secretory granules, where it is accumulated down an electrochemical proton gradient sensitive to the v-ATPase inhibitor bafilomycin A(1). ATP release was partially sensitive to tetanus neurotoxin, whereas glutamate release from the same intoxicated astrocytes was almost completely impaired. Finally, the activation of metabotropic glutamate receptors, which strongly evokes glutamate release, was only slightly effective in promoting purine secretion. These data indicate that astrocytes concentrate ATP in granules and may release it via a regulated secretion pathway. They also suggest that ATP-storing vesicles may be distinct from glutamate-containing vesicles, thus opening up the possibility that their exocytosis is regulated differently.
Coco
Silvia
S
Consiglio Nazionale delle Ricerche Institute of Neuroscience, Cellular and Molecular Pharmacology, Department of Medical Pharmacology, University of Milano, Italy.
Calegari
Federico
F
Pravettoni
Elena
E
Pozzi
Davide
D
Taverna
Elena
E
Rosa
Patrizia
P
Matteoli
Michela
M
Verderio
Claudia
C
D000255:Adenosine Triphosphate / Q000032:analysis / Q000378:metabolism*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001253:Astrocytes / Q000378:metabolism*; D002478:Cells, Cultured; D018698:Glutamic Acid / Q000378:metabolism; D018942:Macrolides; D051381:Rats; D013744:Tetanus Toxin / Q000494:pharmacology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D018942:Macrolides; D013744:Tetanus Toxin; D018698:Glutamic Acid; C040929:bafilomycin A1; D000255:Adenosine Triphosphate; D013755:Tetradecanoylphorbol Acetate