P2Y receptor-mediated enhancement of permeation requires Ca2+ signalling in vascular endothelial cells.

1. We investigated the effects of 2-methylthioATP (2meS-ATP; a P2Y receptor agonist) on the permeation of fluorescein isothiocyanate (FITC)-labelled dextran, transendothelial electrical resistance (TEER) and intracellular calcium levels ([Ca2+]i) in cultured endothelial cells isolated from the rat caudal artery. 2. The cellular transport of FITC-labelled dextran was enhanced and TEER of the endothelial monolayer was reduced by 2meS-ATP. Both these effects were prevented by pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid, a P2Y receptor antagonist, which also inhibited the increase in [Ca2+]i induced by 2meS-ATP in endothelial cells. 3. The increase in [Ca2+]i induced by 2meS-ATP was inhibited by thapsigargin (a Ca2+ pump inhibitor) and by U-73122 (a phospholipase C inhibitor). 4. These findings suggested that activation of the P2Y receptor enhances the passage of material in the endothelium, which is associated with Ca2+ signalling in endothelial cells.