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Calcium signalling through nucleotide receptor P2X1 in rat portal vein myocytes
Author(s) -
Mironneau J.,
Coussin F.,
Morel J. L.,
Barbot C.,
Jeyakumar L. H.,
Fleischer S.,
Mironneau C.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0339c.xd
Subject(s) - ryanodine receptor , receptor , myocyte , intracellular , microbiology and biotechnology , biophysics , calcium , ryanodine receptor 2 , chemistry , vascular smooth muscle , biology , biochemistry , endocrinology , smooth muscle , organic chemistry
1 ATP‐mediated Ca 2+ signalling was studied in freshly isolated rat portal vein myocytes by means of a laser confocal microscope and the patch‐clamp technique. 2 In vascular myocytes held at −60 mV, ATP induced a large inward current that was supported mainly by activation of P2X1 receptors, although other P2X receptor subtypes (P2X3, P2X4 and P2X5) were revealed by reverse transcription‐polymerase chain reaction. 3 Confocal Ca 2+ measurements revealed that ATP‐mediated Ca 2+ responses started at initiation sites where spontaneous or triggered Ca 2+ sparks were not detected, whereas membrane depolarizations triggered Ca 2+ waves by repetitive activation of Ca 2+ sparks from a single initiation site. 4 ATP‐mediated Ca 2+ responses depended on Ca 2+ influx through non‐selective cation channels that activated, in turn, Ca 2+ release from the intracellular store via ryanodine receptors (RYRs). Using specific antibodies directed against the RYR subtypes, we show that ATP‐mediated Ca 2+ release requires, at least, RYR2, but not RYR3. 5 Our results suggest that, in vascular myocytes, Ca 2+ influx through P2X1 receptors may trigger Ca 2+ ‐induced Ca 2+ release at intracellular sites where RYRs are not clustered.