adenosine-5--(n-ethylcarboxamide) and diadenosine-tetraphosphate

The vasoactive properties of P1,P4-diadenosine tetraphosphate (Ap4A) were studied by measuring the effects of perfusion pressure of a rat isolated perfused kidney.. The vasoconstrictive response to Ap4A was mediated to a large extent to a P2X receptor which could be shown by inhibition with pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid tetrasodium. The remaining vasoconstriction of Ap4A could be blocked by a 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), a selective A1 receptor antagonist In raised tone preparation Ap4A evoked vasodilation when P2 receptors were blocked by suramin. The dilation was not mediated by a P2Y receptor as the effect could not be blocked by suramin.. Ap4A induces vasoconstriction via A1 and P2X receptors and vasodilatation via an unidentified receptor which is not a P2Y receptor. Ap4A may play an important role in kidney perfusion and, thus, in blood-pressure control.

Topics: Adenosine Triphosphate; Adenosine-5'-(N-ethylcarboxamide); Animals; Dinucleoside Phosphates; In Vitro Techniques; Male; Perfusion; Pyridoxal Phosphate; Rats; Rats, Inbred WKY; Receptors, Purinergic; Receptors, Purinergic P1; Receptors, Purinergic P2; Renal Artery; Thionucleotides; Vasoconstrictor Agents; Vasodilator Agents; Xanthines