Immunohistochemical and in situ Hybridization Studies on Endothelin in the Rat Eye.

Abstract

To demonstrate the distribution of endothelin (ET) in ocular tissues, we immunohistochemically elucidated the localization of ETs (ET-1, ET-2, ET-3) and their precursors (Big ETs) using specific antibodies that can distinguish precursor and mature types of each isopeptide. ET-A receptor and ET-1 and ET-3 mRNAs were also examined using immunohistochemical and in situ hybridization methods, respectively. Coincidentally, the positive reactivity for ET-1 and ET-3 mRNAs, Big ET-1, Big ET-2, Big ET-3, mature ETs and ET-A receptor was found in almost the same element of the rat ocular tissues, e. g., the retinal neural cells (ganglion, amacrine, bipolar and horizontal cells), the vessel walls in the retina and choroid, the non-pigment epithelium in the ciliary body and iris, the corneal epithelium (anterior surface) and the endothelium (posterior surface), and the epithelium of the lens. These observations indicated that the various ocular tissues biosynthesize and secrete all the isopeptides of ET which act in an autocrine/paracrine fashion, regulating the neural transmission, intraocular pressure, iris smooth muscle tone and ocular blood vessel tone.