Poster presentation, P11
Official XXIst International Pigment Cell Conference website - 21-24 Sept 2011, Bordeaux - France | updated: September 04 2011
Zinc free diet induced a release of melanosomes from choroidal melanocytes and an increase of lipofuscin in the retinal pigment epithelium of rats
SPEAKER | S. Julien #whois submiter ? |
AUTHOR(s) | S. Julien, A. Biesemeier, D. Kokkinou, O. Eibl, U. Schraermeyer |
BACKGROUND AND OBJECTIVES: Age-related macular degeneration (AMD), the leading cause of blindness in the Western world, is associated with lipofuscin accumulation whereas the melanosome content declines. Melanosomes are the main storage of zinc in the pigmented tissues. Since the elderly population, the most affected group for AMD, is prone to zinc deficit, we investigated the chemical and ultrastructural effects of zinc deficiency in pigmented rat eyes after a six-month zinc penury diet. METHODS: Adult Long Evans (LE) rats were used. The control animals (8 LE eyes) were fed with a normal alimentation whereas the zinc-deficiency rats (8 ZD-LE eyes) were fed with a zinc-free diet for six months. Quantitative Electron Dispersive X-ray (EDX) micro-analysis yielded the zinc mole fraction of Retinal Pigment Epithelial (RPE) melanosomes. Light, fluorescence and electron microscopy, as well as immunohistochemistry were performed. The numbers of photoreceptor nuclei, of lipofuscin granules as well as of the cells found in the choroid of ZD-LE rats were quantified. RESULTS: EDX microanalysis showed that RPE melanosomes of untreated LE rats contained 0.04 +/-0.02 at% zinc. In ZD-LE rats, the zinc mole fractions were always at or below the minimum detectable mole fraction of 0.02 at% and therefore significantly lower compared to controls. In contrast, the zinc mole fraction of choroidal melanosomes did not change with respect to controls. The number of photoreceptor nuclei of ZD-LE rats was significantly decreased and the number of the lipofuscin granules was found to be significantly increased in ZD-LE when compared to control rats. Moreover, pigmented ED1-positive cells were detected in the choroid of ZD-LE animals. CONCLUSION: In pigmented animals, the zinc deficiency yields an accumulation of lipofuscin, pigmented macrophages in their choroids and a degeneration of photoreceptors. Moreover, we showed that zinc deficiency reduces the zinc mole fraction of melanosomes in the RPE.