Calcium signalling through nucleotide receptor P2X1 in rat portal vein myocytes.
1. ATP-mediated Ca2+ 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 Ca2+ measurements revealed that ATP-mediated Ca2+ responses started at initiation sites where spontaneous or triggered Ca2+ sparks were not detected, whereas membrane depolarizations triggered Ca2+ waves by repetitive activation of Ca2+ sparks from a single initiation site. 4. ATP-mediated Ca2+ responses depended on Ca2+ influx through non-selective cation channels that activated, in turn, Ca2+ release from the intracellular store via ryanodine receptors (RYRs). Using specific antibodies directed against the RYR subtypes, we show that ATP-mediated Ca2+ release requires, at least, RYR2, but not RYR3. 5. Our results suggest that, in vascular myocytes, Ca2+ influx through P2X1 receptors may trigger Ca2+-induced Ca2+ release at intracellular sites where RYRs are not clustered.
Mironneau
J
J
Laboratoire de Signalisation et Interactions Cellulaires, CNRS UMR 5017, Université de Bordeaux 2, 146 rue Léo Saignat, Bordeaux Cedex 33076, France. jean.mironneau@umr5017.u-bordeaux2.fr
Coussin
F
F
Morel
J L
JL
Barbot
C
C
Jeyakumar
L H
LH
Fleischer
S
S
Mironneau
C
C
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002120:Calcium Channel Agonists / Q000494:pharmacology; D015220:Calcium Channels / Q000276:immunology; D020013:Calcium Signaling / Q000502:physiology*; D015870:Gene Expression / Q000502:physiology; D053496:Inositol 1,4,5-Trisphosphate Receptors; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D018408:Patch-Clamp Techniques; D011169:Portal Vein / Q000166:cytology*; D051381:Rats; D018160:Receptors, Cytoplasmic and Nuclear / Q000276:immunology; D018048:Receptors, Purinergic P2 / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D058469:Receptors, Purinergic P2X; D019837:Ryanodine Receptor Calcium Release Channel / Q000276:immunology; D014544:Uridine Triphosphate / Q000494:pharmacology
D000906:Antibodies; D002120:Calcium Channel Agonists; D015220:Calcium Channels; D053496:Inositol 1,4,5-Trisphosphate Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D018048:Receptors, Purinergic P2; D058469:Receptors, Purinergic P2X; D019837:Ryanodine Receptor Calcium Release Channel; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002118:Calcium; D014544:Uridine Triphosphate