Autoradiographic Localization of 125IEndothelin Binding Sites in Human Blood Vessels and Coronary Tissue

The distribution of endothelin-1 (ET-1) receptors on human vascular tissue has been studied. High- and low-resolution autoradiography was used to determine the distribution of 125ET binding sites in human blood vessels and ventricular myocardium. Dense, displaceable 125IET binding was associated with cardiac myocytes and the smooth muscle layer of all vessels were examined. There was also dense binding to vasa vasora. There was increased 125IET binding to atheromatous coronary arteries and vein graft, which was associated with the tunica media and vasa vasora or regions of neovascularization. Vasoconstrictor and positive inotropic activity of ET-1 has been established in vitro. The vasoconstrictor effect of ET-1 is likely to be mediated via the binding sites identified on vascular smooth muscle. The striking perivascular 125IET-1 binding suggests that ET-1 may also have constrictor activity on vasa vasora. There is experimental evidence that ET-1 has mitogenic activity on vascular smooth muscle cells in culture. The increased binding to both smooth muscle and regions of neovascularization in atheromatous vessels suggests that ET-1 may play a role in atherosclerosis.