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A nucleotide receptor that mobilizes Ca 2+ in the mouse submandibular salivary cell line ST 885
Author(s) -
Gibb C.A.,
Singh S.,
Cook D.I.,
Poronnik P.,
Conigrave A.D.
Publication year - 1994
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1994.tb14863.x
Subject(s) - agonist , extracellular , receptor , nucleotide , suramin , p2 receptor , chemistry , ppads , biology , medicine , endocrinology , biophysics , biochemistry , gene
1 We have identified a Ca 2+ ‐mobilizing receptor that responds to extracellular ATP (0.1–1000 μ m ) in a salivary epithelial cell line (ST 885 ). The activated receptor also stimulates Ca 2+ entry from the extracellular fluid. 2 The receptor shows an agonist selectivity profile consistent with the behaviour of the nucleotide receptor class. In particular, the pyrimidine nucleotide, UTP, was equipotent with ATP. 3 Analysis of concentration‐response data for the ATP and UTP‐activated receptor using the Hill equation yielded EC 50 values (concentrations of agonist inducing a half‐maximal response) for ATP of 4.2 μ m and for UTP of 4.6 μ m . 4 ATP and UTP induced cross‐desensitization and were not additive when administered simultaneously at maximal concentration. These findings are consistent with the hypothesis that both nucleotides act upon a common receptor. 5 The ATP analogue, 2‐methylthio ATP, mobilized Ca 2+ ions with higher potency (EC 50 = 0.23 μ m ) but lower efficacy than either ATP or UTP. However, 2‐methylthio ATP was not a partial agonist of the ATP/UTP receptor. At maximal concentration (30 μ m ), it failed to antagonize the effects of near maximal concentrations of ATP or UTP. We conclude that 2‐methylthio ATP acts upon a distinct receptor.