Endothelin Receptor-Binding Subtypes in the Human Retina and Choroid

Purpose: Endothelins (ETs) are a family of vasoconstrictive peptides produced in part by vascular endothelial cells. They are synthesized in the eye, particularly in the uveal tract, and can markedly constrict the iris and preretinal vessels in the rabbit eye. Two ET receptor subtype families have been characterized and cloned, termed ETAand ETB. To better understand the distribution of ocular ET receptors, we localized ET receptor-binding sites in human and rabbit eyes. Method: Autoradiography with iodine 125-labeled ET-1 and varying concentrations of unlabeled ET-3 was used to localize ET receptor-binding subtypes in the posterior pole of human and rabbit eyes. Results: The ETA-like receptor-binding sites are localized to the retinal and choroidal blood vessels, whereas the ETB-like receptor-binding sites are localized to the neural and glial substance of the retina. Conclusions: Endothelin receptor-binding subtypes are differentially located in the posterior pole of human and rabbit eyes. Endothelin peptides released within the retina and choroid may participate in the ocular manifestations of a variety of systemic disorders, including systemic hypertension.