Endothelin is a potent constrictor of human vessels used in coronary revascularization surgery.

We studied the interaction of endothelin and endothelium-derived relaxing factor (EDRF) in human saphenous veins and internal mammary arteries using isolated ring preparations. Endothelin was a more potent constrictor of human internal mammary arteries and saphenous veins than norepinephrine. The ability of acetylcholine to reverse endothelin-induced contraction was greater in the internal mammary arteries than in saphenous veins. However, nitroprusside produced similar and near-complete inhibition of endothelin precontraction in both arteries and veins. We conclude that endothelin is a potent constricting agent in human internal mammary arteries and saphenous veins in vitro. Endothelin-induced vasoconstriction is effectively inhibited by EDRF, but human saphenous veins appear to have limited capability for endothelium-dependent dilation.