Retinal light-damage in albino rats: Lysosomal enzymes, rhodopsin, and age

The damaging effects incurred during a light-insult on the albino rat retina are studied separately from the resultant loss of visual cells which occurs. Groups of rats, 5–20 weeks of age, are exposed to 48 hr of 80 lax illumination, maintained in the dark for various lengths of time, and then killed. Beginning at light-off and continuing throughout 3 days of darkness, assays are made of (i) outer nuclear layer thickness; (ii) whole retina rhodopsin levels; and (iii) activities of lysosomal proteases known to be important in the degradation of retinal and ocular tissue. It is found that (a) having been given the light-insult, most of the visual cells that will die and disappear do so during the dark, postexposure period; (b) the retinas of all the animals show a limited capability for regenerating rhodopsin after the light-insult but younger animals are somewhat more successful at sustaining this than are older ones; (c) proteolytic enzyme activity is greatest in older animals which are also the ones that lose the most cells.