Effect of atriopeptin II on contrast medium-induced changes in renal blood flow

Volume expansion has been shown to attenuate the vaso-constrictive effects of contrast medium. Since endogenous circulating levels of atrial natriuretic peptides are elevated during volume expansion and since atrial natriuretic peptides have been shown to blunt or block the vasoconstrictive effects of various pharmacologic agents, we examined the effect of atriopeptin II infusion on contrast medium-induced alterations in renal blood flow. Transient changes in renal blood flow were measured with an electromagnetic flow probe following bolus injections of the contrast medium, sodium meglumine diatrizoate (Renovist II, 2 ml/4 sec), into the renal arteries of dogs. Under control conditions (that is, saline vehicle), the bolus of contrast medium caused an initial 15 to 21% increase in renal blood flow at 14 to 21 seconds, followed by a subsequent 5 to 13% decrease in renal blood flow at 43 to 59 seconds after injection. Infusion of atriopeptin II (0.05 pg/kg/min) into the renal artery did not alter arterial blood pressure, glomerular filtration rate, or baseline renal blood flow, but did produce increases in urine flow rate and clearance of sodium. The infusion of atriopeptin II attenuated the contrast medium-induced reduction in RBF, but the infusion of a threshold dose of bradykinin (1 ng/kg/min) had no effect. These results suggest that low doses of atriopeptin II can selectively attenuate the vasoconstrictive effects of contrast medium on renal blood flow without influencing systemic hemodynamics.