Comparative (2)H-labelled alpha-tocopherol biokinetics in plasma, lipoproteins, erythrocytes, platelets and lymphocytes in normolipidaemic males.

The biokinetics of newly absorbed vitamin E in blood components was investigated in normolipidaemic males. Subjects (n 12) ingested encapsulated 150 mg (2)H-labelled RRR-alpha-tocopheryl acetate with a standard meal. Blood was collected at 3, 6, 9, 12, 24 and 48 h post-ingestion. (2)H-Labelled and pre-existing unlabelled alpha-tocopherol (alpha-T) was determined in plasma, lipoproteins, erythrocytes, platelets and lymphocytes by LC-MS. In all blood components, labelled alpha-T concentration significantly increased while unlabelled decreased following ingestion (P<0.0001). Significant differences in labelled alpha-T biokinetic parameters were found between lipoproteins. Time of maximum concentration was significantly lower in chylomicrons, while VLDL had a significantly greater maximum alpha-T concentration and area under the curve (AUC) (P<0.05). The largest variability occurred in chylomicron alpha-T transport. Erythrocyte labelled alpha-T concentrations increased gradually up to 24 h while alpha-T enrichment of platelets and lymphocytes was slower, plateauing at 48 h. Platelet enrichment with labelled alpha-T was biphasic, the initial peak coinciding with the labelled alpha-T peak in chylomicrons. Erythrocyte and HDL AUC were significantly correlated (P<0.005), as was platelet and HDL AUC (P<0.05). There was a lower turnover of pre-existing alpha-T in platelets and lymphocytes (maximum 25 % labelled alpha-T) compared to plasma and erythrocytes (maximum 45 % labelled alpha-T). These data indicate that different processes exist in the uptake and turnover of alpha-T by blood components and that chylomicron alpha-T transport is a major determinant of inter-individual variation in vitamin E response. This is important for the understanding of alpha-T transport and uptake into tissues.