Regional variations in ETA/ETB binding sites in human coronary vasculature.

Endothelin (ET)-1 is an endothelium-derived constrictor peptide that is believed to play a pathophysiologic role in coronary artery disease. Receptors for this peptide have been identified on human coronary tissue by in vitro autoradiography. A number of available compounds are selective for ETA or ETB receptors. Here we have used radiolabeled PD 151242 and BQ 3020 to identify ETA and ETB binding sites on sections of human coronary vasculature. ETA receptors are associated with smooth muscle of the coronary artery. Smooth muscle ETB receptor binding is weak at proximal portions of this vessel but increases toward distal regions. ETB receptors are exclusively associated with myocardial capillaries. Our results indicate that, apart from ETA-induced vasoconstriction, stimulation of ETB receptors at distal regions of the coronary vasculature and myocardial microvessels may play an important role in the pathophysiology of coronary syndromes.