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Lipoproteins were removed from human plasma by ultracentrifugation at a density of 1.225. Three classes of lipoproteins were then separated by 4% Agarose-column chromatography: very low density lipoproteins (VLDL), low-density lipoproteins (LDL), and high-density lipoproteins (HDL). A sensitive high performance liquid chromatography method with a fluorescence detector was used to estimate alpha-tocopherol in plasma and in column eluates. Total plasma tocopherol was not significantly different in males (n = 6) and females (n = 6) and almost all of the vitamin was recovered in the isolated lipoproteins. Although LDL and HDL were the main carriers of alpha-tocopherol in both males and females, more tocopherol was found in LDL than in HDL in males but the opposite was true in females. The distribution of alpha-tocopherol in males was: VLDL, 8%; LDL, 59%; and HDL, 33% whereas that in females was VLDL, 2%; LDL, 42%; HDL, 56%. The distribution of protein in lipoprotein from males was: VLDL, 4%, LDL, 37%; and HDL, 59% and in females: VLDL, 2%; LDL, 25%; and HDL, 73%. The alpha-tocopherol concentration (expressed as microgram alpha-tocopherol/mg protein) in lipoproteins differed little between the sexes. The values in males were: VLDL, 7.0; LDL, 4.3; and HDL, 1.5, in females: VLDL, 3.9; LDL, 4.7; and HDL, 2.1. The data suggest that the different distribution of alpha-tocopherol in plasma lipoproteins in males and females is due to the different levels of proteins in those lipoprotein fractions. Overall, tocopherol and protein levels were highly correlated in HDL, a lower correlation was found in LDL.

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Vitamin E (alpha- and gamma-tocopherol) and total lipid concentrations were determined in the serum of 451 healthy human male and female subjects ranging in age from 19 to 70 years. Mean serum alpha-tocopherol concentration (microgram/ml) was 8.82 +/- 2.84 (SD) and gamma-tocopherol concentration was 1.35 +/- 0.70. The concentration of alpha-tocopherol increased significantly with age, as well as with total lipid; gamma-tocopherol concentration remained unchanged with age. The data also indicated that subjects with higher serum alpha-tocopherol had lower gamma-tocopherol levels and vice versa for subjects with higher gamma levels. A close interrelationship and competition appeared to exist between these two vitamers.

The metabolism of alpha- and gamma-tocopherol was studied in three groups of rats that were fed a modified AIN-76 diet containing normal (NE, 0.2 g alpha-tocopherol/kg), high (HE, 1.0 g alpha-tocopherol/kg) or low (LE, less than 0.02 alpha-tocopherol/kg) vitamin E for 3 mo. After 1, 2 and 3 d of an oral dose of 20 mg of alpha-tocopherol, gamma-tocopherol or both, the levels of the two vitamers were measured in plasma and tissues and in some cases in isolated microsomal and mitochondrial fractions from liver. Twenty-four hours after an oral dose of 20 mg gamma-tocopherol the levels of alpha-tocopherol in plasma and tissues remained constant and higher levels of gamma-tocopherol were found in tissues in which low alpha-tocopherol levels could be found such as in the LE group. In spite of this, it was enabled to remain there, after 2 and 3 d gamma-tocopherol had decreased levels in all tissues. When given in combination with alpha-tocopherol, the levels of gamma-tocopherol were lower than when gamma-tocopherol was given alone. Microsomes and mitochondria from livers of LE group bound five and nine times more alpha-tocopherol than gamma-tocopherol in rats dosed with equal amount of alpha- or gamma-tocopherol, respectively. These data indicate that the mechanisms that regulate the metabolism of vitamin E are highly specific for alpha-tocopherol. Moreover, the relative amount of alpha-tocopherol determined the levels of gamma-tocopherol in tissues. However, the retention of gamma-tocopherol in tissues did not depend on the presence of alpha-tocopherol.(ABSTRACT TRUNCATED AT 250 WORDS)