[Endothelin receptors in bovine retinal vessels--quantitative receptor autographic analysis with radioluminography]

Endothelin (ET) receptors in bovine retinal macrovessels, microvessels, and nonvascular tissues were characterized using a quantitative receptor autoradiographic method with 125I-endothelin-1 (125I-ET-1), ET-1, ET-, ET-3, BQ123 (a selective antagonist for the ETA receptor) and sarafotoxin S6c (an agonist for the ETB receptor). A quantitation was made with a computerized radioluminographic system and imaging plates. The method we used revealed that there were specific binding sites for 125I-ET-1 in the bovine retinal macrovessels, microvessels, and nonvascular tissues. There was no difference in the dissociation constant (Kd) showing binding characteristics between the retinal macrovessels and the microvessels. The bindings to the retinal macrovessels and the microvessels were effectively displaced by BQ123, whereas the binding to the retinal nonvascular tissues was displaced by sarafotoxin S6c. Thus, we obtained evidence that macrovessels and microvessels of the bovine retina have ETA receptor, and that the nonvascular tissues have ETB receptors.