title: Regulation of P2y-purinoceptor-mediated prostacyclin release from human endothelial cells by cytoplasmic calcium concentration.
abstract: 1. ATP and ATP analogues induced prostacyclin (PGI2) secretion from human cultured umbilical vein endothelial cells. 2. The threshold active concentration for ATP was less than or equal to 1 microM. The rank order of potency of analogues was 2-chloroadenosine 5'-triphosphate (2-ClATP) greater than 2-methylthioadenosine 5'-triphosphate (2-MeSATP) greater than ATP greater than ADP, while adenosine 5'-(alpha,beta-methylene)triphosphonate, AMP and adenosine were inactive, indicating the presence of P2y-purinoceptors. 3. In contrast to their actions on P2y-receptors in guinea-pig taenia coli, isopolar analogues of 2-methylthioadenosine 5'-(beta, gamma-methylene)triphosphonate were less effective than ATP. 4. ATP and ATP analogues increased intracellular free calcium ions, [Ca2+]i, giving a rapid transient peak due predominantly to release from intracellular stores, followed by a maintained steady-state elevated level due to influx. 5. The dose-response curves for peak [Ca2+]i induced by ATP, 2-ClATP and 2-MeSATP were very similar to those for PGI2 production. 6. Elevations of [Ca2+]i, above a threshold value of 0.8-1 microM, were necessary for PGI2 production in response to P2y-receptor activation. 7. The dose relationships between PGI2 release and peak [Ca2+]i were equivalent whether [Ca2+]i was raised by ionomycin or via P2y-receptor activation by ATP or 2-ClATP, indicating that elevations of [Ca2+]i provide the major, if not the exclusive intracellular pathway for P2y-purinoceptor-mediated PGI2 synthesis.
authors.affiliation: Section of Vascular Biology, MRC Clinical Research Centre, Harrow, Middx.
authors.forename: T D
authors.initials: TD
authors.lastname: Carter
authors.forename: T J
authors.initials: TJ
authors.lastname: Hallam
authors.forename: N J
authors.initials: NJ
authors.lastname: Cusack
authors.forename: J D
authors.initials: JD
authors.lastname: Pearson
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D003593:Cytoplasm / Q000378:metabolism; D004730:Endothelium, Vascular / Q000187:drug effects / Q000502:physiology*; D011464:Epoprostenol / Q000378:metabolism*; D006801:Humans; D011983:Receptors, Purinergic / Q000187:drug effects / Q000502:physiology*
chemical_list: D011983:Receptors, Purinergic; D000255:Adenosine Triphosphate; D011464:Epoprostenol; D002118:Calcium