Exogenous Endothelin-1 Causes Renal Vasolidation in the Fetal Lamb

AbstractPurpose: Endothelin-1 is known to be a potent vasoconstrictor. We investigated the effects and mechanisms of action of endothelin-1 and its receptors in regulating renal vascular tone in the fetal lamb.Materials and Methods: We observed the in vivo effects of endothelin-1, and endothelin-b receptor agonist (4-alanine-endothelin-1), endothelin-a receptor antagonists (BQ-610 and BQ-123), and the inhibition of prostaglandin and nitric oxide synthesis on the response of the renal circulation to endothelin-1 in a chronic preparation in third trimester fetal lambs.Results: After injection of 250 ng./kg. endothelin-1 into the descending aorta proximal to the renal arteries in 8 fetal animals, renal blood flow increased (4.4 plus/minus 0.7 ml. per minute per kg., p less than 0.001 versus vehicle), as did mean arterial blood pressure (3.0 plus/minus 0.3 mm. Hg, p less than 0.001 versus vehicle). Calculated renal vascular resistance decreased (-1.1 plus/minus 0.2 mm. Hg per minute per kg./ml., p less than 0...