P2 Receptors in Blood Vessels

Abstract

Extracellular purines and pyrimidines regulate blood flow by important effects on vascular tone mediated via cell surface P2 receptors. P2 receptors are divided into two superfamilies, P2X and P2Y, according to whether they are ligand-gated cation channels or are coupled to G proteins respectively. Seven P2X and at least five P2Y receptors have been cloned to date. Members of both the P2X and the P2Y receptor families are expressed by blood vessels, being found on the smooth muscle, endothelium and perivascular nerves, where they are associated with specific effects on vascular tone. P2 receptors in blood vessels include smooth muscle P2X1 receptors, which have an important role as mediators of vasoconstriction owing to ATP released as a cotransmitter from sympathetic perivascular nerves, and endothelial P2Y1 (or P2y) and P2Y2 (or P2U) receptors which mediate vasodilatation. Vasodilator P2Y and contractile uridine nucleotide-specific receptors have been described in some vascular smooth muscles. This chapter describes the different subtypes of P2 receptors in blood vessels and examines the way in which the responses that they mediate integrate in the control of vascular tone.