Trace metals in human retina during aging period

Age-related macular degeneration (ARMD) is the principal cause of blindness in modern countries after 50 years (28% prevalence after 75 years). In ARMD pathology, a progressive degeneration of retinal photoreceptors appears in the region of macula which is responsible of high resolution and colour vision. Oxidative stress is probably implicated in ARMD development. Since iron can induce free radical formation during aging and is known to contribute to cerebral neurodegenerative diseases, we investigate iron homeostasis in the different layers of the human retina. In this study were determined iron and other trace metals and minerals concentrations and their tissue lateral distribution in post-mortem retina of aged people (43 to 95 years). Special iron homeostasis proteins (transferrin, transferrin receptor, ferritin), which control iron transport, uptake and storage, were also studied in human retina and showed the same spatial distribution as in the rat retina. For trace metals determination, the frozen eyeballs were cut at low temperature in thin sections of 20 µm, collected on the rasor-blade of a cryomicrotome, placed on FormvarR foils and freeze-dried before analysis. We used then simultaneously Proton-Induced X-Ray Emission (PIXE) and Rutherford Backscattering Spectrometry (RBS) methods with the Bordeaux proton microprobe to determine the metal contents of retina. A post-irradiation coloration of the tissue sections allows us to identify precisely the retina layers and to produce local spectra in each layer. Detailed technique and preliminary results will be presented.