Endothelin-1 is a potent constrictor in conductive and resistive coronary arteries.

The action of endothelin-1 (ET-1) in canine and porcine coronary artery ring preparations and perfused canine and porcine myocardium was examined in vitro to determine the site of action of ET-1 in the coronary vasculature. ET-1 had a vasoconstrictor effect that was more potent in smaller diameter ring preparations. The EC50s for both canine and porcine ring preparations decreased with a decrease in vessel diameter and the EC50 of ET-1 in the perfused myocardium was three to four times lower than in the smallest ring preparation. The results suggest that ET-1 may cause cardiac ischemia by constriction of resistive vessels rather than by epicardial coronary artery spasm.