[Vitamin E: comparison of efficiency of incorporation of alpha-tocopherol in the organs in comparison to gamma-tocopherol].

Refeeding rats deficient in vitamin E with alpha-tocopherol induces increased amount of this compound in brain, cerebellum, sciatic nerve and muscle. This increase is regular with time. The optimum level (corresponding to non-deficient animals) is not reached within 8 weeks after refeeding. Thus recovery is very slow for the nervous tissue (as it has been demonstrated for polyunsaturated fatty acids). In contrast, the optimum level is reached within 2 weeks for liver and serum. Refeeding rat deficient in vitamin E with gamma-tocopherol induces an increase of this compound in the liver, the plateau is reached within 2 weeks, but is clearly lower than the one obtained with alpha-tocopherol : approximately 4 times lower. In the muscle, the uptake is linear with time, the plateau is not reached within 8 weeks, its level is 4 times lower than with alpha-tocopherol. Important point : feeding animals deficient in vitamin E with gamma-tocopherol induces in the nervous system a level of gamma-tocopherol which is not the one of the residual alpha-tocopherol; the plateau is not reached within 8 weeks. In sciatic nerve and cerebellum (but not in the brain) increased amount of gamma-tocopherol as a function of time is parallel with a slight but significant reduction of the residual alpha-tocopherol. In another experiment, rats were fed a diet deficient with vitamin E until 60 days of age. From this age, they received a non deficient diet until 120 days. In all organs, increasing the ratio gamma/alpha tocopherol (with a constant amount of alpha-tocopherol) induces an increase of alpha-tocopherol. This result is unexpected, as it was possible to propose that gamma-tocopherol could reduce alpha-tocopherol utilisation by competition. Conversely, the presence of alpha-tocopherol seems to increase incorporation of gamma-tocopherol, except in brain and sciatic nerve. The presence of gamma-tocopherol seems to induce increased need of alpha-tocopherol. This specificity for alpha-tocopherol is very important in terms of nutrition and pharmacology. In fact, at least to preserve biological membranes, it is important to provide only alpha-tocopherol, and not other molecules.