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Two distinct P2Y receptors are involved in purine‐ and pyrimidine‐evoked Ca 2+ elevation in mammalian brain astrocytic cultures
Author(s) -
Bolego Chiara,
Centemeri Carlo,
Abbracchio Maria P.,
Ceruti Stefania,
Cattabeni Flaminio,
Jacobson Kenneth A.,
Puglisi Lina,
Rovati Gian Enrico,
Burnstock Geoffrey,
Nicosia Simonetta
Publication year - 2001
Publication title -
drug development research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.582
H-Index - 60
eISSN - 1098-2299
pISSN - 0272-4391
DOI - 10.1002/ddr.1106
Subject(s) - p2y receptor , pertussis toxin , homologous desensitization , receptor , medicine , endocrinology , thapsigargin , extracellular , phospholipase c , biology , purinergic receptor , chemistry , agonist , biochemistry , g protein
ATP and 2‐methyl‐thio‐ATP (2‐Me‐SATP) increase cytosolic calcium concentrations ([Ca 2+ ] i ) in rat striatal astrocytes (Centemeri et al. [1997] Br J Pharmacol 121:1700–1706). The aim of the present study was to: (1) characterize pyrimidine‐induced [Ca 2+ ] i increases in the same experimental system, and (2) try to identify the multiple P2Y receptor subtypes mediating Ca 2+ mobilization. UDP and UTP triggered a concentration‐dependent [Ca 2+ ] i elevation (EC 50 s = 0.58 μM ± 0.4 and 31 μM ± 6, respectively). Pyrimidine‐evoked [Ca 2+ ] i elevation was solely due to mobilization from intracellular stores, because: (1) removing calcium from extracellular medium or (2) blocking its influx with Ni 2+ did not modify UTP responses; (3) the store‐depleting agent thapsigargin completely abolished UTP‐evoked [Ca 2+ ] i increments. Guanosine‐5′‐O‐(2‐thiodiphosphate) partially inhibited the UTP response, whereas pertussis toxin (PTx) had no effect. The phospholipase C inhibitor U‐73122 significantly reduced the UTP‐evoked [Ca 2+ ] i rise. Computer‐assisted analysis indicated that the UTP and UDP responses are mediated by a single receptor, while ATP and 2‐Me‐SATP interact with two distinct receptors. The selective P2Y 1 receptor antagonist MRS2179 abolished the ATP higher potency component. Sequential challenges with the same nucleotides resulted in almost complete homologous desensitization. Pre‐exposure to UTP lowered the subsequent responses to either ATP or 2‐Me‐SATP. Maximally active concentrations of UTP and ATP were not additive. In conclusion, [Ca 2+ ] i elevation in astrocytes by purines and pyrimidines is mediated by two distinct P2Y receptors, likely the P2Y 1 and P2Y 6 subtypes. Drug Dev. Res. 52:122–132, 2001. © 2001 Wiley‐Liss, Inc.