Coronary Vascular Nitric Oxide Activity in Hypertension and Hypercholesterolemia Comparison of Acetylcholine and Substance P

Background Whether the abnormal responses of the human coronary circulation to acetylcholine in patients with hypertension and hypercholesterolemia extend to other, nonmuscarinic stimulators of the endothelium and whether this signifies a specific abnormality of NO is not known. Methods and Results We studied 26 patients with angiographically normal coronary arteries, 10 without risk factors, and 16 with either hypertension (n=9) and/or hypercholesterolemia (n=10). Dose-response curves were performed with acetylcholine, substance P, and sodium nitroprusside before and after NG-monomethyl-l-arginine (L-NMMA). Substance P produced predominantly epicardial coronary dilation, whereas the dilating effect of acetylcholine was mainly microvascular. There was no correlation between the responses to the two drugs. L-NMMA did not affect the response to sodium nitroprusside, but it suppressed dilation in response to both substance P and acetylcholine, suggesting that the latter promote bioavailability of NO from the...