Localisation of endothelin-1 mRNA expression and immunoreactivity in the retina and optic nerve from human and porcine eye. Evidence for endothelin-1 expression in astrocytes.

We have investigated the localisation of endothelin-1 (ET-1) mRNA and ET-1-like immunoreactivity in retina and anterior portion of optic nerve from human and porcine eyes. In situ hybridisation method revealed expression of ET-1 mRNA mainly in the innermost layers of the retinas, in the retinal pigment epithelium cells as well as in the astrocytes of the optic nerve. Immunohistochemical studies showed that ET-1-like immunoreactivity appeared in the same regions where ET-1 mRNA was expressed as well as in the inner nuclear layer and in the inner segments of photoreceptors. In the nerve fibre and ganglion cell layers, astrocytes expressed both glial fibrillary acidic protein and ET-1 proteins suggesting that these cells may secrete ET-1. Expression of ETA and ETB receptors in human retina were demonstrated by reverse transcription-polymerase chain reaction. Our results demonstrated expression of ET-1 in glial, neural and vascular components of retina and optic nerve from human and porcine eyes.