How selective antagonists and genetic modification have helped characterise the expression and functions of vascular...

Vascular P2Y receptors mediate many effects, but the role of individual subtypes is often unclear. Here we discuss how subtype-selective antagonists and receptor knockout/knockdown have helped identify these roles in numerous species and vessels. P2Y₁ receptor-mediated vasoconstriction and endothelium-dependent vasodilation have been characterised using the selective antagonists, MRS2179 and MRS2216, whilst AR-C118925XX, a P2Y₂ receptor antagonist, reduced endothelium-dependent relaxation, and signalling evoked by UTP or fluid shear stress. P2Y₂ receptor knockdown reduced endothelial signalling and endothelial P2Y₂ receptor knockout produced hypertensive mice and abolished vasodilation elicited by an increase in flow. UTP-evoked vasoconstriction was also blocked by AR-C118925XX, but the effects of P2Y₂ receptor knockout were complex. No P2Y₄ receptor antagonists are available and P2Y₄ knockout did not affect the vascular actions of UTP and UDP. The P2Y₆ receptor antagonist, MRS2578, identified endothelial P2Y₆ receptors mediating vasodilation, but receptor knockout had complex effects. MRS2578 also inhibited, and P2Y₆ knockout abolished, contractions evoked by UDP. P2Y₆ receptors contribute to the myogenic tone induced by a stepped increase in vascular perfusion pressure and possibly to the development of atherosclerosis. The P2Y₁₁ receptor antagonists, NF157 and NF340, inhibited ATP-evoked signalling in human endothelial cells. Vasoconstriction mediated by P2Y₁₂/P2Y₁₃ and P2Y₁₄ receptors was characterised using the antagonists, cangrelor, ticagrelor, AR-C67085 and MRS2211 or PPTN respectively. This has yet to be backed up by receptor knockout experiments. Thus, subtype-selective antagonists and receptor knockout/knockdown have helped identify which P2Y subtypes are functionally expressed in vascular smooth muscle and endothelial cells and the effects that they mediate.