Extracellular ATP increases [Ca2+]i in primarily cultured pig coronary smooth muscle cells via a P2Y purinoceptor subtype.
In primarily cultured pig coronary smooth muscle cells, extracellular adenosine triphosphate (ATP; 10(-9) to 10(-3) M) dose-dependently increases intracellular calcium ([Ca2+]i). The [Ca2+]i transients measured by fura-2 fluorescence consist of peak and plateau phases with [Ca2+]i values of 191.84 +/- 5.67 nM (n = 10) and 91.67 +/- 1.89 nM, respectively. In Ca(2+)-free solution, the peak phases persisted, but there was a loss of the plateau response, indicating an initial ATP-stimulated intracellular Ca2+ release and a subsequent transarcolemmal Ca2+ entry. Various agonists have been used to characterize the P2 purinoceptor subtype involved in the ATP-induced Ca2+ transients. The rank order of potency was uridine triphosphate (UTP) > ATP >> 2-meSATP > beta,gamma-meATP = alpha,beta-meATP = adenosine = 0. To examine the refilling of ATP-sensitive stores, four repetitive 60-s ATP responses were produced throughout with a 5-min recovery period in between. Now the ATP peaks gradually declined in Ca(2+)-free solution, indicating the emptying of the stores. If, however, Ca2+ entry was allowed in the "refilling period" (i.e., between the ATP pulses), the Ca2+ peaks could be maintained or restored, respectively. The data suggest that the ATP-dependent [Ca2+]i transients may be mediated via a UTP > ATP-activated P2Y purinoceptor subtype, mediating both an intracellular Ca2+ release and a transarcolemmal Ca2+ influx. The refilling of Ca2+ stores may occur through the unstimulated membrane after agonist stimulation. A putative pathway may be a "capacitative" Ca2+ entry induced on depletion of intracellular Ca2+ stores.
Seiler
L
L
Department of Physiology I, Albert-Ludwigs-University, Freiburg, Germany.
Matyas
S
S
Fleckenstein-Grün
G
G
D000241:Adenosine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000378:metabolism* / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D005110:Extracellular Space / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D058906:Purinergic P1 Receptor Agonists; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058473:Receptors, Purinergic P2Y2; D013498:Suramin / Q000494:pharmacology; D013552:Swine; D013873:Thionucleotides / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000494:pharmacology
D058906:Purinergic P1 Receptor Agonists; D058910:Purinergic P2 Receptor Agonists; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058473:Receptors, Purinergic P2Y2; D013873:Thionucleotides; C005147:5'-adenylyl (beta,gamma-methylene)diphosphonate; D013498:Suramin; D000255:Adenosine Triphosphate; D000241:Adenosine; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D002118:Calcium; D014544:Uridine Triphosphate; C008501:2-methylthio-ATP