Deficiencies of vitamins E and A in the rat. Retinal damage and lipofuscin accumulation

The interrelationships of vitamins E and A in maintaining various structural components of the retina were studied in four groups of weanling female rats fed purified diets adequate or deficient in each vitamin: +E, +A; -E, +A; +E, -A; and -E, -A. Groups deficient in retinol (-A) were supplemented with retinoic acid. After 14, 21, and 35 weeks, the retinas were examined histologically and ultrastructurally. At 35 weeks, the doubly deficient rats (-E, -A) had lost 92% of their rod nuclei, whereas rats deficient in vitamins A (+E, -A) or E (-E, +A) alone had lost only 34% and 20%, respectively. Vitamin E deficiency resulted in extensive lipofuscin deposits in the retinal pigment epithelium as early as 21 weeks, but the presence of vitamin A doubled the number of lipofuscin granules (-E, +A vs. -E, -A) and induced an even greater increase in their autofluorescence. Another clear influence of vitamin A was seen when +E, +A retinas autofluoresced not only much more than +E, -A retinas, which had similar numbers of granules, but also more than -E, -A retinas, which had about twice as many lipofuscin granules. In the retina, unlike the uterus, the lipofuscin-specific autofluorescence and lipofuscin granule number were not proportional. Moreover, the numbers of granules were influenced by both vitamins E and A, whereas the intensity of lipofuscin-specific autofluorescence was determined almost exclusively by vitamin A. Probably the accelerated loss of photoreceptor cells in -E, -A retinas resulted from both oxidation of membranes and oxidation of retinal vitamin A stores in the absence of vitamin E protection.