Endothelins act via two receptor subtypes, endothelin receptor type A (ETA ) and type B (ETB ). Under physiological conditions in coronary arteries ETA receptors expressed in smooth muscle cells mediate vasoconstriction whereas ETB receptors mainly found in endothelial cells mediate vasorelaxation. However, under pathophysiological conditions ETB receptors may also be expressed in vascular smooth muscle cells mediating vasoconstriction. We aimed to investigate whether vasoconstrictor ETB receptors are upregulated in coronary arteries after experimental myocardial ischemia in rats.