Muller cells in developing rats with inherited retinal dystrophy

Morphology and enzymes of Muller cells in the developing retina of RCS (Royal College of Surgeons) rats were investigated. RCS (rdy/rdy) rats with inherited retinal dystrophy were studied and RCS (+/+) rats served as normal controls. Rats underwent intracardiac perfusion with 4% paraformaldehyde and the eyes were enucleated on postnatal days P1, 4, 10, 21, 35, and 100. Eyes were then fixed with 4% paraformaldehyde, and silver enhancing technique was applied to show glutamine synthetase (GS) and glial fibrillary acidic protein (GFAP). For solubilized retinas, Western blot analysis and enzyme-linked immunosorbent assay (ELISA) were performed to detect GS and GFAP in the extracts. Immunohistochemistry showed GS expression first on P10. It increased later in both normal and dystrophic retinas. GFAP was not expressed in normal retinas, but Muller cells of dystrophic retinas were stained on P35 and P100. GS immunoblots were recognized on P21 and later in both normal and dystrophic retinas with similar densities, while GFAP immunoblots were observed only on P35 and P100, and only in dystrophic retinas. ELISA demonstrated increased GS concentrations with the development in both normal and dystrophic retinas, but no significant difference was observed between them. GFAP concentrations had no significant difference on P21 between both groups, those of normal ones remained unchanged later, while those of dystrophic rats were remarkably increased on P35 and P100. Muller cells might be affected following the progressive degeneration of photoreceptor cells and react to the glio-neuronal relationship. (C) 2000 Tohoku University Medical Press.