STRUCTURAL AND BIOCHEMICAL-CHANGES IN VITAMIN-A-DEFICIENT RAT RETINAS

  • 1 January 1979
    • journal article
    • research article
    • Vol. 18  (5) , 437-446
Abstract
The levels of rhodopsin and opsin were investigated in relation to the maintenance of retinal structure in retinas of vitamin A-deficient rats reared in low levels of cyclic illumination (1.5-2 ft-c). Rhodopsin levels decreased in the deficient retinas to approximately 20% of control at 9 wk, and this level was retained through 39 wk on the deficient diet. Opsin levels decreased at a slower rate but reached about 20% of control levels at 32 wk. Despite the decrease in rhodopsin levels, obvious deterioration of disc structure was not observed until 16 wk of deficiency, when opsin levels had already decreased to 60-70% of control. The structural disruption of photoreceptor outer segments was localized initially in discs of the distal 3rd. Rod cell degeneration preceded cone cell degeneration in vitamin A-deficient retinas. Most of the rods and cones persisted in the posterior retina at 23 wk on the deficient diet; however, by 40 wk, only 11% of the rod nuclei remained. In contrast, about 63% of the cone nuclei were present at 40 wk of deficiency. The photoreceptor cells were affected by the deficiency to a greater extent in the inferior hemisphere than in the superior hemisphere of the eye.