Renal vascular effects of dilazep antagonized by 3-isobutyl-1-methyl-xanthine.

The effects of different doses of dilazep on renal hemodynamics, urine formation, and renin release were studied in anesthetized dogs. Intrarenal arterial infusion of dilazep (1 microgram/kg/min) increased renal blood flow, with no change in systemic arterial blood pressure and renal venous plasma renin activity. Renal vasodilation induced by dilazep was completely inhibited by intrarenal arterial infusion of 3-isobutyl-1-methyl-xanthine (IBMX; 11.1 micrograms/kg/min), a potent adenosine receptor antagonist, but not by indomethacin (13 mg/kg i.v.). These results suggest that dilazep has a vasodilatory action in the kidney--one that is independent of the renal renin-angiotensin system. The inhibitory action of IBMX on the dilazep-induced renal vasodilation indicates that the renal vascular effects of dilazep may be exerted by augmentation of endogenous adenosine and mediated through adenosine receptors.