Abstract
The effects of the natural antioxidant vitamin E and synthetic antioxidant ethoxyquin on the ageing process were studied in rats from 21 to 702 days after birth. Two dose levels of vitamin E, 0.05% and 0.5%, and ethoxyquin 0.5%, were used in the diet. In the long term study, the body weight gain of animals receiving diets containing both 0.05% and 0.5% vitamin E were greater than those of either pair-fed or ad-libitum fed controls and this suggests that the control diet was suboptimal with respect to its vitamin E content although the symptoms of vitamin E deficiency were not present. Early reduction in body weight gain in the 0.5% ethoxyquin-treated group was due to impaired palatability rather than impaired food utilisation because a similar growth rate was seen in the pair-fed controls. Later, however, the fall in the food intake and body weight correlated with the occurence of kidney damage. The liver and kidney weight of ethoxyquin-treated animals were significantly higher than in pair-fed controls. The kidney of the ethoxyquin-treated animals in the long term study showed chronic nephritis. In the short term study of two months, 0.5% ethoxyquin in the diet did not show nephrotoxicity. No abnormalities were seen in the kidneys of animals receiving vitamin E in the diet. The histology of bones of rats fed ethoxyquin for a long time suggested less deposition of calcium. In the short term study the humerus of ethoxyquin-fed rats contained a significantly lower level of calcium than in pair-fed controls and the bone weight was also significantly lower. In the long term study of antioxidants, both 0.5% vitamin E and ethoxyquin in the diet caused a significant reduction in PCV and a significant increase in the circulating reticulocytes. Ethoxyquin also significantly increased the clotting time. In the short term study, animals receiving the diets containing 0.05% vitamin E and 0.5% ethoxyquin contained significantly more reticulocytes than pair-fed controls. The clotting time was higher in antioxidant-treated animals, but the difference only reached statistical significance in the case of the 0.5% vitamin E treated animals. The accumulation of lipofuscin pigment in the brain of rats in the long term study shoved a significantly lover intensity of fluorescence in animals that received both 0.5% vitamin E and ethoxyquin in the diet, in spite of the fact that the entry of [14]C ethoxyquin into the brain seemed to be small. The possible relevance of this work to longevity and the ageing process is discussed.