Endothelin- and neuropeptide Y-induced vasoconstriction of human epicardial coronary arteries in vitro.

1. The effects of the recently discovered peptide endothelin and neuropeptide Y (NPY) on human epicardial coronary arteries were studied in vitro. 2. Endothelin induced a concentration-dependent, endothelium-independent, long-lasting vasoconstriction regardless of vessel size. NPY evoked contractions of small coronary arteries with a similar potency to that of endothelin, although to a significantly lower degree. Large coronary arteries did not respond to NPY. Endothelin did not relax coronary arteries precontracted with potassium. 3. The effect of endothelin was dependent on extracellular Ca2+ and, like NPY, significantly reduced by the Ca2+-antagonist nifiedipine. 4. In conclusion, endothelin is a potent human vasoconstrictor in vitro. It is suggested that endothelin may be involved in the regulation of coronary blood flow.