1. Endogenous endothelin (ET) does contribute to control of renal vascular
tone via nitric oxide (NO)-dependent vasodilation in the rat,
2. Endothelin mediates some of the renal vascular responses to acute nitric
oxide synthase (NOS) inhibition, being particularly important when a rise
in renal perfusion pressure occurs,
3. Tonically produced NO blunts the renal vasoconstrictor responses to acut
ely administered ET.
4. The similarity between the renal vascular responses to ET administration
and NOS inhibition is not fortuitous but, in part, reflects important inte
ractions between these vasoactive agents.