Effects of FR139317 on renal responses to acute nitric oxide blockade in anaesthetized rats

1. Effects of FR139317, an endothelin ETA receptor antagonist, on renal haemodynamic and excretory responses to acute nitric oxide (NO) blockade were examined using anaesthetized rats. 2. Intrarenal arterial infusion of NG-nitro-L-arginine (NOARG), the NO synthase inhibitor, at a rate of 40 micrograms/kg per min, produced a significant decrease in renal blood flow, with no change in systemic blood pressure. There were significant decreases in urine flow and urinary excretion of sodium during infusion of NOARG. In animals pretreated with FR139317, similar renal responses to the NOARG infusion were observed. 3. These results suggest that an action of endothelin-1 via ETA receptors does not greatly contribute to the renal haemodynamic and excretory responses to acute blockade of renal NO production.