Differential effects of diadenosine phosphates on purinoceptors in the rat isolated perfused kidney

Abstract

1. The activation of various purinoceptors in rat renal vasculature by P¹,P²-diadenosine pyrophosphate (Ap₂A), P¹,P³-diadenosine triphosphate (Ap₃A), P¹,P⁴-diadenosine tetraphosphate (Ap₄A), P¹,P⁵-diadenosine pentaphosphate (Ap₅A), P¹,P⁶-diadenosine hexaphosphate (Ap₆A) was studied by measuring their effects of perfusion pressure of a rat isolated perfused kidney.

2. The vasoconstrictive response to Ap₅A was completely due to P_2X purinoceptor activation, that to Ap₄A and Ap₆ was P_2X purinoceptor mediated to a large extent, as evidenced by the inhibitory effects of suramin and pyridoxal-phosphate-6-azophenyl-2′,4′-disulphonic acid tetrasodium (PPADS).

3. The vasoconstrictive effects of Ap₂A and Ap₃A were mostly due to stimulation of A₁-receptors, as shown by the inhibitory effect of 8-cyclopentyl-1,3-dipropylxanthine (DPCPX).

4. The vasoconstrictive response to Ap₆A was partially insensitive to A₁ and P_2X purinoceptor blockers.

5. In raised tone preparations Ap₂A and Ap₃A evoked vasodilatation, which was blocked by the A₂ receptor blocker, 3,7-dimethyl-1-propargylxanthine (DMPX).

6. In raised tone preparations Ap₄A evoked vasodilatation when the P₂-purinoceptors were blocked by suramin.

7. The activation of different purinoceptor subtypes by diadenosine phosphates critically depends on the number of phosphate groups.

Full Text

The Full Text of this article is available as a PDF (408.8 KB).