Specific desensitization of the canine renal vasculature to angiotensin II despite cyclo-oxygenase inhibition.

Intrarenal angiotensin (AII) infusion results in a poorly sustained renal vasoconstrictor response. To examine the relationship between fade and renal tachyphylaxis to AII, sub-pressor doses of AII and norepinephrine (NE) were injected into the renal arteries of anesthetized dogs, resulting in a transient reduction (greater than 50 percent) in renal blood flow. Continuous intrarenal AII infusion, sufficient to reduce renal blood flow by 50 percent, followed. Within five minutes, despite continued AII infusion, substantial recovery (73 +/- 11 percent) of renal blood flow occurred; however, the response to AII bolus injection was lost, but that to NE was sustained. A second group of dogs received indomethacin (5 mg/kg intravenously) 30 minutes prior to the study; the reduction in renal blood flow was better sustained; however, renal tachyphylaxis was still evident.