The Influence of Alpha-Tocopherol Upon the Utilization of Carotene and Vitamin A

Abstract

The addition of 0.5 mg α-tocopherol daily to the diet of partially depleted rats receiving 35 to 129 µg vitamin A daily for 14 or 28 days produced no significant change in the liver stores of vitamin A, except in one group on the lowest level of intake for 28 days. Above a 75-µg daily intake of vitamin A, the liver storage was nearly quantitatively cumulative. Addition of 0.5 mg α-tocopherol supplement daily to the diet of similar rats given 24 to 174 µg of carotene in oil daily for 14 or 28 days produced a significant increase in liver vitamin A when the total carotene intake was from 1,200 to 2,400 µg, or the daily intake from 87 to 174 µg for 14 days. Above and below these levels no effect was found. No cumulative storage of vitamin A was found at any level of dosing. A consistent but small decrease in growth was seen in the groups which received tocopherol with carotene and profited by it in regard to liver vitamin A. This appeared also in the vitamin A-fed rats, even though the effect on liver vitamin A was negligible. A later experiment in which 1.0-mg daily doses of α-tocopherol were used as well as 0.5-mg ones indicated that there was no difference in the effectiveness of these levels. In this series the tocopherol produced small and perhaps insignificant increases in liver but not in kidney deposits of vitamin A. The total store of vitamin A in these animals was in all cases only slightly greater than the daily dosage. The peak of vitamin A content in the intestinal wall was found to occur two hours after carotene in water dispersion had been given, and after three hours no vitamin A was present in the intestine. Vitamin A was also always found in the intestine after two hours but not after three hours in the experiments with carotene in oil. The speed of disappearance may be related to the magnitude of the dose. An interfering substance which produced a pinkish color instead of the blue of vitamin A with the antimony trichloride reagent appeared in the intestine at 15 minutes and three hours after the carotene dosing and at no other time. This may be caused by an intermediate in the carotene-to-vitamin-A reaction. Carotene in aqueous solution (Tween 40) produced larger amounts of liver vitamin A than carotene in the oily medium, but tocopherol was ineffective or depressant under these conditions.