EXPRESSION OF THE PROTECTIVE PROTEINS HEMOPEXIN AND HAPTOGLOBIN BY CELLS OF THE NEURAL RETINA

The blood-retinal barrier, consisting of retinal pigment epithelial ce lls and retinal endothelial cells, prevents hemopexin and haptoglobin, anti-oxidant protective plasma proteins normally synthesized by the l iver, from entering the neural retina. If present, these proteins must , therefore, be made locally. The cell types within the retina in whic h hemopexin and haptoglobin mRNAs are made have been investigated, RNA was extracted from both the neural retina and pigment epithelium obta ined by dissection of human donor eyes as well as from cultured pigmen t epithelial and photoreceptor cells. The mRNAs for both haptoglobin a nd hemopexin were detected, using reverse-transcriptase polymerase cha in reaction, in the neural retina and cultured photoreceptors but not in pigment epithelial cells. The cellular location of these mRNAs was determined using in situ hybridization of sections of human retina whi ch revealed that haptoglobin mRNA was located principally in the photo receptor cells, cells of the inner nuclear layer and some cells of the ganglion cell layer, Hemopexin mRNA, previously shown to be made in t he human neural retina (Hunt et al., 1996. Journal of Cellular Physiol ogy 168: 71-80), is expressed by most of the cells of neural retina in cluding the photoreceptors and, notably, the ganglion cells. (C) 1998 Academic Press.