EFFECTS OF FR139317 ON RENAL RESPONSES TO ACUTE NITRIC-OXIDE BLOCKADEIN ANESTHETIZED RATS

1. Effects of FR139317, an endothelin ETA receptor antagonist, on rena l haemodynamic and excretory responses to acute nitric oxide (NO) bloc kade were examined using anaesthetized rats. 2. Intrarenal arterial in fusion of N-G-nitro-L-arginine (NOARG), the NO synthase inhibitor, at a rate of 40 mu g/kg per min, produced a significant decrease in renal blood how with no change in systemic blood pressure. There were signi ficant decreases in urine how and urinary excretion of sodium during i nfusion of NOARG, In animals pretreated with FR139317, similar renal r esponses to the NOARG infusion were observed. 3. These results suggest that an action of endothelin-1 via ETA receptors does not greatly con tribute to the renal haemodynamic and excretory responses to acute blo ckade of renal NO production.