Graded dietary levels of RRR-gamma-tocopherol induce a marked increase in the concentrations of alpha- and gamma-tocopherol in nervous tissues, heart, liver and muscle of vitamin-E-deficient rats.

The effect of dietary RRR-gamma-tocopherol supplementation on serum and tissue alpha- and gamma-tocopherol concentrations was studied in vitamin-E-deficient rats fed diets containing adequate levels of RRR-alpha-tocopherol and graded levels of RRR-gamma-tocopherol over a 60 day period. Feeding rats with a RRR-alpha-tocopherol-supplemented diet induced in forebrain, sciatic endoneurium, skeletal muscle, heart and liver a marked increase in alpha-tocopherol concentration. In contrast, feeding rats with a diet containing the same level of RRR-gamma-tocopherol induced a small increase in gamma-tocopherol concentrations in brain, sciatic endoneurium, skeletal, muscle, heart and liver and a slight but significant decrease in alpha-tocopherol concentration in all tissues examined. In rats fed diets containing a constant level of RRR-alpha-tocopherol and graded levels of RRR-gamma-tocopherol, the concentrations of alpha-tocopherol in all tissues were much higher than those in rats fed a control diet containing RRR-alpha-tocopherol alone. The higher the gamma/alpha ratio, the more the alpha-tocopherol concentrations increased. Significant positive linear regressions were found between the gamma/alpha ratio and the alpha- and gamma-tocopherol concentrations in most of the tissues examined. These results indicate that when gamma-tocopherol was supplied continuously in the diet gamma-tocopherol accumulated significantly in the tissues but to a much smaller extent than when rats were fed with RRR-alpha-tocopherol. These experiments also indicate that gamma-tocopherol did not depress the serum and tissue alpha-tocopherol concentrations. On the contrary, gamma-tocopherol supplements induced a marked increase in alpha-tocopherol concentrations in the serum and tissues. These results suggest that there is a relationship between alpha- and gamma-tocopherol levels in vivo and that the biopotency of alpha-tocopherol should be reevaluated especially when high levels of gamma-tocopherol were present in the diet.