Role of endothelin-1 in the active constriction of human atherosclerotic coronary arteries

Background-Atherosclerotic coronary arteries are prone to constriction but the underlying causes are incompletely understood. We tested the hypothesis that endothelin-1 (ET-1), a potent vaso constrictor, contributes to the heightened tone of atherosclerotic human coronary arteries. Methods and Results-In 8 patients with coronary artery disease (CAD) and 8 patients with angiographically smooth coronary arteries (normal), we infused BQ-123, an antagonist of the ETA receptor, into a major coronary artery (infused artery) at 40 nmol/min for 60 minutes. The infused artery in the CAD patients contained a >50% stenosis. Using, quantitative angiography, we compared the dilation of the infused artery with another, noninfused coronary artery. To estimate the magnitude of the contribution of ET-1 to coronary tone, we compared the dilation to BQ-123 with that elicited by intracoronary nitroglycerin (200 mug). BQ-123 induced significant dilation in the normal arteries (7.3% at 60 minutes, P<0.001 versus noninfused arteries) and a greater dilation in the CAD arteries (16.3% at 60 minutes, P<0.001 versus infused normal arteries). The dilation at stenoses was particularly pronounced (21.6% at 60 minutes, P<0.001 versus infused CAD arteries). Compared with the dilation from nitroglycerin, ET-1 contributed to 39% of the coronary tone in normal arteries, 74% of tone in CAD arteries, and 106% of tone at stenoses (P<0.01). Conclusions-ET-1 accounts for nearly all the resting tone in atherosclerotic coronary arteries, especially at stenoses. Inhibitors of ET-1, by relieving constriction, may significantly lessen the hemodynamic significance of coronary stenoses and thereby reduce myocardial ischemia.