The Purinergic Agonists ATP and UTP Act Predominantly via P2Y Receptors in Human Vascular Endothelial Cells

Purinergic agonists, such as ATP, can produce robust vasodilation, yet the specific receptor(s) (i.e. P2X or P2Y) responsible for these effects remain poorly characterized. In this study, we have examined the purinergic receptors mediating acute Ca 2+ mobilization, membrane hyperpolarization and nitric oxide (NO) synthesis in cultured HUVECs (EA.hy926 cell line). Brief application of either ATP or UTP (2 μM) to single HUVECs produced comparable elevations in cytosolic Ca 2+ , membrane hyperpolarizations and acute NO synthesis. These responses were largely unaffected in the presence of the non‐selective P2X receptor antagonists PPADS (10 μM) and TNP‐ATP (1 μM). In contrast to ATP and UTP, the selective P2X receptor agonist α,β‐methyl ATP (2 μM) had little effect on cytosolic Ca 2+ , membrane potential or NO production. Collectively, these data suggest that the observed stimulatory actions of ATP and UTP in this cell system occur primarily via P2Y, and not P2X, receptors. A plot of the concentration‐dependent rise in cytosolic Ca 2+ evoked by ATP and UTP revealed similar EC50 values for the two agonists (1–3 μM); this equipotent action of ATP and UTP further suggests that P2Y2 receptors are the predominant purinergic sub‐type. Finally, RT‐PCR analysis confirmed the presence of P2Y2 receptor mRNA in this human vascular endothelial cell model. Research support to AP Braun was provided by the CIHR and HSF Alberta