Chronic retinal effects by ultraviolet irradiation, with special reference to superoxide dismutases

Abstract

Recently ultraviolet light (UV) reaching the Earth's surface has been gradually increasing in amounts by the destruction of the ozone layers. Large parts of UV are absorbed in the cornea and lens, and only a few amounts reach the retina; however, the effect on the retina is not fully elucidated. 38 rats were irradiated 0.5- 5.0 ~ / c mUV~ f rom 6 to 50 times every 24 hours, and their retinal effects were investigated morphologicaily, immunohistochemically and immunochemically for superoxide dismutases (SOD). Morphologically, the destruction of rod outer segments (ROS) and dissociation of cell membranes between the pigment epithelial cells (PE) were already observed by 6 times 0.5 ~ / c mUV~ i rradiations. As the doses of UV increased, heterochromatins and lipid droplets increased in the PE. Significant damage was not observed, except in ROS and PE. In normal retina, CuIZn SOD were mainly distributed from the inner limiting membrane (ILM) to the ganglion cell layer, and the PE; however, after 6 times 0.5 ~ / c mUV~ i rradiations, the distribution became widened from inner to outer plexiform layer (OPL). At that time, the concentrations of CuKn and Mn SOD increased in the retina. The present study reveals that the morphological damage caused by UV irradiation is observed in the ROS and PE, where no immunoreactivities could be detected to CuIZn and Mn SOD. However, morphological damage was not from the ILM to OPL, where the imrnunoreactivities to both Cu/Zn and Mn SOD were observed.