ATP-induced ATP release from astrocytes.
Propagation of interastrocyte Ca2+ waves is mediated by diffusion of extracellular adenosine triphosphate (ATP), and may require regenerative release of ATP. The ability of ATP to initiate release of intracellular ATP was assessed by labeling adenine nucleotide pools in astrocyte cultures with 14C-adenine. The 14C-purines released during exposure to ATP were then identified by thin-layer chromatography. ATP treatment caused a five-fold increase in release of 14C-ATP but not 14C-ADP or 14C-AMP, indicating selectivity for release of ATP. Other P2 receptor agonists also caused significant 14C-ATP release, and the P2 receptor antagonists suramin, reactive blue-2 and pyridoxalphosphate-6-azo(benzene-2,4-disulfonic acid) (PPADS) inhibited ATP-induced 14C-ATP release to varying degrees, suggesting the involvement of a P2 receptor. ATP-induced 14C-ATP release was not affected by chelation of intracellular Ca2+ with BAPTA-AM, or by blockers of Ca2+ release from intracellular stores or of extracellular Ca2+ influx, suggesting a Ca2+-independent response. ATP-induced 14C-ATP release was significantly inhibited by non-selective anion channel blockers but not by blockers of ATP-binding cassette proteins, gap junction hemichannels, or vesicular exocytosis. Release of adenine nucleotides induced by 0 Ca2+ was, in contrast, not selective for ATP, and was susceptible to inhibition by gap junction blockers. These findings indicate that astrocytes are capable of ATP-induced ATP release and support a role for regenerative ATP release in glial Ca2+ wave propagation.
Anderson
Christopher M
CM
Department of Neurology, University of California, San Francisco and Department of Veterans Affairs Medical Center, San Francisco, California 94121, USA. candrsn@mail.ucsf.edu
Bergher
Jennifer P
JP
Swanson
Raymond A
RA
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology*; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism*; D001557:Benzenesulfonates / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002250:Carbon Radioisotopes; D002478:Cells, Cultured; D002855:Chromatography, Thin Layer; D045604:Extracellular Fluid / Q000378:metabolism; D017629:Gap Junctions / Q000187:drug effects; D007424:Intracellular Fluid / Q000378:metabolism; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D009544:Niflumic Acid / Q000494:pharmacology; D058919:Purinergic P2 Receptor Antagonists; D011687:Purines / Q000032:analysis / Q000378:metabolism; D018048:Receptors, Purinergic P2 / Q000378:metabolism; D013379:Substrate Specificity; D013498:Suramin / Q000494:pharmacology
C110258:4,4,',4'',4'''-(carbonylbis(imino-5,1,3-benzenetriylbis(carbonylimino)))tetrakis(benzene-1,3-disulfonate); D001557:Benzenesulfonates; D002250:Carbon Radioisotopes; D007473:Ion Channels; D058919:Purinergic P2 Receptor Antagonists; D011687:Purines; D018048:Receptors, Purinergic P2; D009544:Niflumic Acid; D013498:Suramin; D000255:Adenosine Triphosphate; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D002118:Calcium