Effect of adenosine on isolated afferent arterioles

We investigated the direct effect of adenosine on afferent arterioles(Af-Arts) and the receptor subtype that mediates the constrictor or dilator action of adenosine. Af-Arts were isolated from the superficial cortex of rabbit kidney and perfused in vitro. Adenosine added to either the-lumen or bath constricted the Af-Arts in a dose-dependent manner. This constriction was blocked by the A, receptor antagonist, 6-oxo3-(2-phenylpyrazole(l, 5-a)pyridin-3-yl)-l (6H)-pyridazinebutyric acid (FK838) or 8-cyclopentyl-l, 3-dipropyIxanthine(DPCPX). We also examined the effect of adenosine on preconstricted Af-Arts with norepinephrine. Adenosine added to either the lumen or bath further constricted the preconstricted AfArts. In the presence of FK838, adenosine added to either the lumen or bath dilated the preconstricted AfArts, but in a different dose-dependent manner. Adenosine-induced dilation was inhibited by the A2 receptor antagonist, 3, 7-dimetyl-l-propargylxanthine(DMPX). These data indicate that adenosine constricts Af-Arts via A, receptors and that adenosine dilates preconstricted Af-Arts via A2 receptors when A! receptors are blocked.