Vasodilatation by acetylcholine is endothelium-dependent: a study by sonomicrometry in canine femoral artery in vivo.

Abstract

External diameter of the femoral artery was measured by sonomicrometry in the anaesthetized dog. Intra-arterial acetylcholine lowered arterial pressure and thereby passively lowered diameter. When blood flow and distal resistance were controlled by roller pump and Starling resistor respectively, acetylcholine (0.1-10 microM) and substance P (0.1-1 nM) both caused up to 10% increase in diameter. Removal of endothelium by mechanically rubbing the artery lumen abolished the dilator response to acetylcholine and substance P but did not affect the response to nitroprusside. Constrictor responses to noradrenaline were unaltered by endothelium removal. Topical application of acetylcholine and subst..