Cellular and subcellular patterns of expression of bFGF and CNTF in the normal and light stressed adult rat retina.

This study compared the distributions in the normal and light stressed rat retina of the neuroprotective factors bFGF (basic fibroblast growth factor) and CNTF (ciliary neurotrophic factor). Albino Sprague-Dawley rats were raised in cyclic light and some were exposed to bright continuous light for 48 hr, to induce light damage of photoreceptors. Their retinas were prepared as cryosections, immunolabelled with antibodies to bFGF and CNTF and analysed by confocal microscopy. Both factors were prominent in macroglial cells (astrocytes, Müller cells) and the retinal pigment epithelium (RPE). In the somas of these cells the distributions of the two factors were complementary, with bFGF concentrated in the nuclei and CNTF in the cytoplasm. Both factors were distributed along the processes of macroglial cells, in granular form. CNTF was not detected in neurones, but bFGF was consistently present in the cytoplasm of ganglion cell somas and, in regions of retina subject to stress, in the cytoplasm of photoreceptors. bFGF was not detected in the nuclei or processes of neurones. In retina stressed by light exposure or proximity to the anterior edge of the retina, the levels of bFGF and CNTF were up-regulated, without major changes in localization. Macroglial cells (Müller cells, astrocytes) play a major role in distributing bFGF and CNTF throughout the retina. The different localizations of the two factors within the somas of macroglial, RPE and photoreceptor cells, suggest that their protective actions are exerted by distinctive mechanisms.