Mediation of the vasoactive properties of diadenosine tetraphosphate via various purinoceptors

Objective and methods The vasoactive properties of P-1,P-4-diadenosine tetr aphosphate (Ap(4)A) were studied by measuring the effects of perfusion pres sure of a rat isolated perfused kidney. Results The vasoconstrictive response to Ap(4)A was mediated to a large ext ent to a P-2X receptor which could be shown by inhibition with pyridoxal-ph osphate-6-azophenyl-2',4'-disulfonic acid tetrasodium. The remaining vasoco nstriction of Ap(4)A could be blocked by a 8-cyclopentyl-1,3-dipropylxanthi ne (DPCPX), a selective A(1) receptor antagonist. In raised tone preparatio n Ap(4)A evoked vasodilation when P-2 receptors were blocked by suramin. Th e dilation was not mediated by a P-2Y receptor as the effect could not be b locked by suramin. Conclusion Ap(4)A induces vasoconstriction via A(1) and P-2X receptors and vasodilatation via an unidentified receptor which is not a P-2Y receptor. A p(4)A may play an important role in kidney perfusion and, thus, in blood-pr essure control. J Hypertens 1998, 16:1939-1943 (C) 1998 Lippincott Williams & Wilkins.