The effect of the ETA receptor antagonist, FR 139317, on [125I]‐ET‐1 binding to the atherosclerotic human coronary artery

1 The distribution of [125I]‐endothelin (ET‐1) binding sites on atherosclerotic human epicardial coronary arteries has been studied by in vitro receptor autoradiography. 2 [125I]‐ET‐1 binding was to the tunica media and regions of neovascularization. 3 Competition studies were carried out in the presence of ET‐1 and the ETA receptor antagonist, FR 139317. The IC50 values for ET‐1 at the tunica media and regions of neovascularization were similar (mean ± s.e.mean of n = 4 patients, 2.5 ± 0.9 nm and 2.9 ± 0.9 nm, respectively) whereas IC50 values for FR 139317 at regions of neovascularization (607 ± 34 nm) were significantly higher than those of the tunica media (12.6 ± 2.4 nm) (P < 0.0001). 4 These results indicate that ETA receptors are present on the tunica media of the diseased human coronary artery whereas a different ET receptor subtype exists at regions of neovascularization.