Role for intrarenal adenosine in the renal hemodynamic response to contrast media

The intrarenal injection of contrast media results in a transient fall in renal blood flow (RBF) and a decrease in glomerular filtration rate (GFR). These effects are enhanced by dietary sodium restriction and attenuated by sodium loading. A similar sodium-dependent response of RBF and GFR occurs with the intrarenal injection of adenosine. In view of these similarities, we sought to determine whether endogenous adenosine is involved in the renal hemodynamic response to contrast media. The intrarenal injection of contrast media (meglumine-Na diatrizoate, 76%) in six sodium-depleted, anesthetized dogs resulted in a 17% +/- 4% decrease in RBF and a 31% +/- 5% decrease in GFR. The infusion of the adenosine receptor antagonist, theophylline (5 mumol/min), reduced the decrease in RBF to 6% +/- 2% and in GFR to 12% +/- 3% of control values. During the intrarenal infusion of dipyridamole (24 micrograms/kg/min), a potentiator of adenosine through its action to inhibit the cellular uptake of nucleosides, the hemodynamic response to contrast media was greater; RBF fell 25% +/- 4% and GFR fell 44% +/- 7%. In addition, the urinary excretion of endogenous adenosine increased after the injection of contrast media (388 +/- 79 vs. 830 +/- 231 nmol/min). In summary, the contrast media-induced fall in RBF and GFR was attenuated by theophylline and augmented by dipyridamole, and the administration of contrast media resulted in an increase in the excretion of endogenous adenosine. These results support the hypothesis that endogenous adenosine is involved in the renal hemodynamic response to contrast media.