ENDOTHELIN-LIKE IMMUNOREACTIVITY AND RECEPTOR-BINDING IN THE CHOROID AND RETINA

This study has examined the localisation and receptor-binding of the e ndothelins in retina and choroid of human and rat origin. Immunoreacti vity to anti-ET1 and anti-ET3 was investigated in trypsin digests, fro zen sections and ultrathin sections using immunocytochemistry and immu nogold labelling techniques. In addition, receptor binding of I-125-ET 1 and I-125-ET3 was visualised and quantified using autoradiography an d image analysis. Intense immunoreactivity to anti-ET1 and anti-En was observed in the photoreceptor inner segments and in the outer plexifo rm layer (OPL) of human and rat retina. Ultrastructural localisation u sing immunogold labelling confirmed the presence of ET1 and ET3 in the photoreceptor cells. In retinal vascular digests, ET1 was visualised in the arteries, arterioles and at the pre-arteriolar sphincters, howe ver, immunoreactivity to anti-ET3 was absent in the retinal vasculatur e. Both ET(A) and ET(B)-type receptor binding sites to I-125-ET1 and I -125-ET3 were detected in the vascular smooth muscle of choroidal and retinal vessels with the former being predominant. Extravascular bindi ng sites of the ET(B)-type were found in the ganglion cell layer.