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P2Y purinoceptor activation mobilizes intracellular Ca 2+ and induces a membrane current in rat intracardiac neurones
Author(s) -
Liu DongMei,
Katnik Christopher,
Stafford Mark,
Adams David J.
Publication year - 2000
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.1469-7793.2000.00287.x
Subject(s) - ppads , cyclopiazonic acid , suramin , p2y receptor , purinergic receptor , phospholipase c , pertussis toxin , thapsigargin , medicine , extracellular , biology , endocrinology , adenosine , uridine triphosphate , endoplasmic reticulum , biophysics , g protein , receptor , biochemistry , nucleotide , gene
1 The mobilization of Ca 2+ by purinoceptor activation and the relative contributions of intra‐ and extracellular sources of Ca 2+ were investigated using microfluorimetric measurements of fura‐2 loaded in cultured neurones from rat intracardiac ganglia. 2 Reverse transcriptase‐polymerase chain reaction (RT‐PCR) revealed expression of mRNA for the G protein‐coupled P2Y 2 and P2Y 4 receptors. 3 Brief application of either 300 μ m ATP or 300 μ m UTP caused transient increases in [Ca 2+ ] i of 277 ± 22 nM and 267 ± 39 nM, respectively. Removal of external Ca 2+ did not significantly reduce these [Ca 2+ ] i responses. 4 The order of purinoceptor agonist potency for [Ca 2+ ] i increases was ATP = UTP > 2‐MeSATP > ADP >> adenosine, consistent with the profile for P2Y 2 purinoceptors. ATP‐ and UTP‐induced rises in [Ca 2+ ] i were completely and reversibly blocked by 10 μ m PPADS (a P2 purinoceptor antagonist) and partially inhibited by 100 μ m suramin (a relatively non‐specific purinoceptor antagonist). 5 In the presence of the endoplasmic reticulum Ca 2+ ‐ATPase inhibitor cyclopiazonic acid (10 μ m ) in Ca 2+ ‐free media, the [Ca 2+ ] i responses evoked by ATP were progressively decreased and abolished. 6 ATP‐ and UTP‐induced [Ca 2+ ] i rises were insensitive to pertussis toxin, caffeine (5 m m ) and ryanodine (10 μ m ) but were significantly reduced by U‐73122, a phospholipase C (PLC) inhibitor. 6 In fura‐2‐loaded cells, perforated patch whole‐cell recordings show that ATP and UTP evoked slow outward currents at ‐60 mV, concomitant with the rise in [Ca 2+ ] i , in approximately 30 % of rat intracardiac neurones. 7 In conclusion, these results suggest that in rat intracardiac neurones, ATP binds to P2Y 2 purinoceptors to transiently raise [Ca 2+ ] i and activate an outward current. The signalling pathway appears to involve a PTX‐insensitive G protein coupled to PLC generation of IP 3 which triggers the release of Ca 2+ from a ryanodine‐insensitive Ca 2+ store(s).