The Endothelium — Modulator of Vascular Smooth-Muscle Tone

Furchgott and Zawadzki1 first reported that endothelial cells have an obligatory role in the relaxation caused by acetylcholine in isolated rabbit arteries. This observation reconciled earlier contradictory findings of the powerful vasodilatory effect of acetylcholine in the intact organism, as compared with the contraction that it causes in spiral strips of isolated blood vessels in which the endothelium has been damaged or removed. There has followed an exponential growth in knowledge about the role of the endothelium in modulating the tone of the underlying smooth muscle in response to pharmacologic agents, physiologic stimuli, and disease.2 3 4 The function of the endothelium . . .