ENDOTHELIN RECEPTOR-BINDING SUBTYPES IN THE HUMAN RETINA AND CHOROID

Purpose: Endothelins (ETs) are a family of vasoconstrictive peptides p roduced 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 sub type families have been characterized and cloned, termed ET(A) and ET( B). To better understand the distribution of ocular ET receptors, we l ocalized ET receptor-binding sites in human and rabbit eyes. Method: A utoradiography with iodine 125-labeled ET-1 and varying concentrations of unlabeled ET-3 was used to localize ET receptor-binding subtypes i n the posterior pole of human and rabbit eyes. Results: The ET(A)-like receptor-binding sites are localized to the retinal and choroidal blo od vessels, whereas the ET(B)-like receptor-binding sites are localize d to the neural and glial substance of the retina. Conclusions: Endoth elin receptor-binding subtypes are differentially located in the poste rior pole of human and rabbit eyes. Endothelin peptides released withi n the retina and choroid may participate in the ocular manifestations of a variety of systemic disorders, including systemic hypertension.