LOCALIZATION OF ENDOTHELIN-LIKE IMMUNOREACTIVITY AND ENDOTHELIN BINDING-SITES IN RABBIT EYES

Immunohistochemistry and in vitro autoradiographic techniques were use d to investigate the localization of endothelin (ET)-like immunoreacti vity and [I-125]ET-1 binding sites in sections of ocular tissues of no rmal rabbits. ET-like immunoreactivity was localized to the corneal en dothelium and the pre-epithelial layer of the cornea, which was specif ically inhibited by addition of exogenous ET-1. Immunoreactivity for E T was also observed in the retinal ganglion layer and periocular fat t issues. These, however, were not inhibited in the presence of ET-1. Au toradiography showed binding sites for ET-1 in the iris and ciliary bo dy. Emulsion-dipped slides of sections of rabbit eyes incubated with [ I-125]ET-1 showed specific labeling for binding sites over structures that were identified from serial sections stained with hematoxylineosi n. These were the anterior stroma of the iris root, the walls of capil laries, the circular arteries, and the veins of the ciliary body and e xtraocular muscles. No binding sites were found in the cornea or conju nctiva. The difference in regional distributions of ET storage and bin ding sites in rabbit ocular tissue suggests that the peptide may have specific physiologic functions.