Acetylcholine causes endothelium-dependent dilation of normal arteries in most animal species. The effect of acetylcholine on normal human coronary arteries is controversial. Pathologic studies and epicardial echocardiography have shown that diffuse atherosclerosis is often present despite angiographic evidence of discrete coronary artery disease (CAD). Therefore, we postulated that acetylcholine would cause vasoconstriction of coronary arteries that are angiographically normal in patients with CAD. Coronary artery diameter, measured by automated quantification of digitized cineangiograms, was determined before and after the intracoronary infusion of 0.2 mM acetylcholine at 0.8-1.6 ml/min. The diameter of stenotic or irregular segments of six atherosclerotic coronary arteries decreased from 1.80±0.42 mm before acetylcholine to 1.26±0.46 mm after acetylcholine (p=0.0025). Acetylcholine had a significantly diYferent effect on the diameter of two groups of coronary arteries that are angiographically normal. Acetylcholine caused a 0.16±0.09-mm increase in the diameter of 14 normal coronary arteries in patients without CAD, whereas it caused a 0.26+0.12-mm decrease in the diameter of 14 normal coronary arteries in patients with CAD (p <0.01). Thus, the normal response to intracoronary acetylcholine is vasodilation, suggesting that endotheliumderived relaxing factor is released from normal human coronary endothelium. The vasoconstrictive effect of acetylcholine in the angiographically normal coronary arteries of patients with CAD suggests the presence of a diffuse abnormality of endothelial function. (Circulation 1989;79:287-291) T here is growing evidence that acetylcholine and a number of other substances induce vasodilation by stimulating the release of an endothelium-derived relaxing factor (EDRF) from endothelial cells, whereas nitroglycerin and other endothelium-independent vasodilators induce vasodilation through the direct stimulation ofvascular smooth muscle."2,3 Thus, acetylcholine or aggregating platelets cause relaxation of arteries with an intact endothelium but cause contraction of arteries denuded of endothelium.1"2'3 An impairment of endotheliumdependent vasodilation has been observed in rabbits4 and monkeys5'6 that were fed an atherogenic diet. atherosclerosis and restored endothelium-dependent relaxation to normal.6 Conflicting data exist, however, regarding the existence of endothelium-mediated vasodilation in human coronary arteries. Several in vitro studies conclude that acetylcholine and carbachol, both muscarinic agonists, constrict human coronary arteries,7-10 whereas other studies suggest that acetylcholine dilates normal human coronary arteries.1" Similarly, a discrepancy exists regarding the effect of acetylcholine on human coronary arteries in vivo. After the intracoronary infusion of acetylcholine, Horio et al12 observed at least a 25% decrease in the diameter of normal or almost normal coronary arteries in 27 of 70 arteries, whereas Ludmer et al13 reported an 11% increase in the diame...

There is growing evidence that reperfusion of ischemic organs is associated with the formation of free radicals that exacerbate the ischemic injury. Free radicals may damage viable tissue via the peroxidation of lipids and oxidation of protein sulfhydryl groups, leading to perturbations of membrane permeability and enzyme function. Steven Werns and Benedict Lucchesi discuss evidence that activated neutrophils are an important source of free radicals after cardiac and intestinal ischemia, and assess the strategies that have been investigated as ways of alleviating damage caused by free radicals during ischemia-reperfusion.

Six months of cholesterol-lowering therapy has no significant effect on coronary endothelial vasomotor function in the study population of patients with coronary artery disease and mildly elevated cholesterol levels. These findings suggest that the effects of cholesterol lowering on endothelial function are more complex than previously thought.