Increase of [Ca(2+)](i) via activation of ATP receptors in PC-Cl3 rat thyroid cell line.
In PC-Cl3 rat thyroid cell line, ATP and UTP provoked a transient increase in [Ca(2+)](i), followed by a lower sustained phase. Removal of extracellular Ca(2+) reduced the initial transient response and completely abolished the plateau phase. Thapsigargin (TG) caused a rapid rise in [Ca(2+)](i) and subsequent addition of ATP was without effect. The transitory activation of [Ca(2+)](i) was dose-dependently attenuated in cells pretreated with the specific inhibitor of phospholipase C (PLC), U73122. These data suggest that the ATP-stimulated increment of [Ca(2+)](i) required InsP(3) formation and binding to its specific receptors in Ca(2+) stores. Desensitisation was demonstrated with respect to the calcium response to ATP and UTP in Fura 2-loaded cells. Further studies were performed to investigate whether the effect of ATP on Ca(2+) entry into PC-Cl3 cells was via L-type voltage-dependent Ca(2+) channels (L-VDCC) and/or by the capacitative pathway. Nifedipine decreased ATP-induced increase on [Ca(2+)](i). Addition of 2 mM Ca(2+) induced a [Ca(2+)](i) rise after pretreatment of the cells with TG or with 100 microM ATP in Ca(2+)-free medium. These data indicate that Ca(2+) entry into PC-Cl3 stimulated with ATP occurs through both an L-VDCC and through a capacitative pathway. Using buffers with differing Na(+) concentrations, we found that the effects of ATP were dependent of extracellular Na(+), suggesting that a Na(+)/Ca(2+) exchange mechanism is also operative. These data suggest the existence, in PC-Cl3 cell line, of a P2Y purinergic receptor able to increase the [Ca(2+)](i) via PLC activation, Ca(2+) store depletion, capacitative Ca(2+) entry and L-VDCC activation.
Marsigliante
Santo
S
Laboratory of Physiology, Department of Biology, University of Lecce, Lecce 73100, Italy. smarsi@ilenic.unile.it
Elia
Maria Giovanna
MG
Di Jeso
Bruno
B
Greco
Simona
S
Muscella
Antonella
A
Storelli
Carlo
C
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D020746:Calcium Channels, L-Type / Q000502:physiology; D020013:Calcium Signaling; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004963:Estrenes / Q000494:pharmacology; D007700:Kinetics; D009543:Nifedipine / Q000494:pharmacology; D011760:Pyrrolidinones / Q000494:pharmacology; D051381:Rats; D018048:Receptors, Purinergic P2 / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000502:physiology; D014544:Uridine Triphosphate / Q000494:pharmacology
D002121:Calcium Channel Blockers; D020746:Calcium Channels, L-Type; D004791:Enzyme Inhibitors; D004963:Estrenes; D011760:Pyrrolidinones; D018048:Receptors, Purinergic P2; C060229:1-(6-((3-methoxyestra-1,3,5(10)-trien-17-yl)amino)hexyl)-1H-pyrrole-2,5-dione; D000255:Adenosine Triphosphate; D012964:Sodium; D010738:Type C Phospholipases; D009543:Nifedipine; D002118:Calcium; D014544:Uridine Triphosphate