VITAMIN A AND CAROTENE UTILIZATION IN PROTEIN-DEPRIVED RATS

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Abstract
Maintenance of rats on a protein-free, but not a 4% casein, diet produced a significant lowering of serum vitamin A. This effect was seen in rats deprived of vitamin A or provided with 90 μg of the vitamin twice weekly. In a separate study, rats maintained on 4% and 20% casein diets were depleted of vitamin A. They were then given 6 or 12 μg of vitamin A or 24 μg of carotene per day. The blood vitamin A response to administered vitamin A was not affected. Rats fed the low-protein diet exhibited only about one half of the serum vitamin A response to administered carotene as did those fed the 20% casein diet. Carotene failed to maintain liver vitamin A content in rats fed the low-protein diet. The results suggested that the absorption/conversion of β-carotene is impaired in rats maintained on a 4% protein diet. When rats were fed a protein-free diet the mobilization of vitamin A from the liver, or transport of the vitamin was also impaired.