Studies are proposed to continue and extend findings relevant to the pathological effects of visible light in retinal photoreceptor cells and in the retinal pigment epithelium (RPE) of rats. We will study the mechanism of light damage by determining the temporal sequence of antioxidative enzyme inactivation i n rod outer segments (ROS) isolated from light exposed rats and the loss od docosahexaenoic acid from ROS membranes. The protective effect of ascorbic acid on ROS enzymes and lipids will be measured in normal rats exposed to continuous light or to short light-dark periods and in ROS isolated at various times in the dark period following light exposure. Peroxidation of ROS membranes will be examined as the causative factor of light exposure. Peroxidation of ROS membranes will be examined as the causative factor of light damage by measureing the extent of rhodopsin loss and peroxide accumulation in the retinas of rats with depleted docosahexaenoic acid in their ROS. The protective effects of reduced ROS docosahexaenoate and ascorbate against light damage will be examined in combination, in rats, with the aim of further reducing, or eliminating, light damage to the retina. The same experimental paradigm of light exposures will be used to determine the sequence of photoreceptor cell and RPE cell membrane damage. Because of the differences in the extent of photoreceptor and RPE cell damage from light between cyclic light and dark reared normal rats and young and older dystrophic rats these will be our experimental animals. We will determine the extent of RPE cell membrane involvement during light damage by isolating RPE plasma membranes and measuring membrane enzymes and lipids. Both glass beads and bead-bound monoclonal antibodies against RPE plasma membrane proteins will be used to isolate the membranes from light damaged rats. Correlative light and electron microscopic studies will be performed on the eyes of light damaged rats. We will supply monoclonal antibodies by collaborative arrangement to begin functional studies of RPE plasma membrane protiens in normal and dystrophic rat RPE cells in tissue culture. Our studies in the temporal sequence of light damage in retina and between retina and RPE in the rat will provide insights into the mechanism of light damage in this model and can be extended to scorbutic animals in which ascorbate has also been shown to be protective. These studies are seen as being relevant to the prevention of light damage in the human eye, especially during periods of intense light exposure as occurs with increasing frequency in surgical settings and in the work place.