Light induced retinal degeneration and corticosterone treatment.

E.M. LOPEZ, H. COIRNI AND J.J. LOPEZ-COSTA

Buenos Aires

Congreso; VII Jornadas Multitudinarias de la Sociedad Argentina de Biolog¨ªa (SAB).; 2005

Light induced retinal degeneration and corticosterone treatment L¨®pez EM.1, H Coirini H.2 and L¨®pez-Costa JJ.1 1IBCyN ¡§Prof. E. De Robertis¡§, 2IBYME, 2Dept Bioqu¨ªmica Humana, Facultad de Medicina, UBA-CONICET, Buenos Aires, Argentina. Email:estermarialopez@yahoo.com Continuous illumination (CI) induces retinal degeneration (RD) and increases glucocorticoid (GC) levels because it is a stressful condition. Our previous results have shown that adrenalectomy delayed RD induced by CI. The aim of the present work was to evaluate the relationship between different doses of CORT and its effect on the retina of adrenalectomized (ADX) rats. Adult male Sprague Dawley rats were ADX and submitted to CI (12000 lux) during 5 days. Along the illumination, animals were daily subcutaneously injected with either a high dose of CORT (HD-CORT= 4 mg/kg), a low dose of CORT (LD-CORT= 0.4 mg/kg), or vehicle (ADX-VH). Rats were sacrificed under anesthesia; eyes were fixed with 4% paraformaldehyde and embedded in paraplast. Sections were stained with hematoxylin-eosin and retinal thickness was determined using a Kontron-Vidas image analyzer. Data was statistically analyzed using the Student Newman-Keuls Multiple comparison test. After 5 days of illumination, retinal thickness of HD-CORT rats (167.3 ¡À 9.46 ¦Ìm) was significantly thinner than in ADX-VH rats (193.21¡À9.06 ¦Ìm p<0.001) or  than in LD-CORT rats (192.06 ¡À 8.83 ¦Ìm; p <0.001). No differences were found in the retinal thickness between LD-CORT rats and ADX-VH rats (p > 0.05). In summary, high doses of CORT contribute to RD while low doses seem to be innocuous. The present results support the idea that a stressful situation may contribute to the deleterious effect of CI due to high circulating levels of steroids (Supported by UBACYT-M20).