TRANSPORT OF ALPHA-TOCOPHEROL AND BETA-CAROTENE IN HUMAN-BLOOD

Abstract

The concentrations and distributions of major lipids (cholesterol, phospholipid and triglyceride), tocopherol and carotenoids were determined in the plasma lipoprotein fractions (VLDL, LDL and HDL) of normal human subjects, patients with hyperlipoproteinemia and patients with erythropoietic protoporphyria treated with oral .beta.-carotene and/or .alpha.-tocopherol. The distribution of tocopherol (in percent) was most closely correlated with the distribution of total lipids in the individual lipoproteins, while the major portion of .beta.-carotene was present in the low density lipoproteins, irrespective of the lipid distribution in the lipoproteins (except for one subject with hyperchylomicronemia). The .alpha.-tocopherol and .beta.-carotene concentrations of plasma and RBC in patients treated with tocopherol and carotene were determined periodically for a 1-yr period. Plasma and RBC tocopherol concentrations showed a rapid, parallel increase in response to tocopherol supplementation. The plasma and RBC carotene concentrations showed a much slower and nonparallel increase in response to carotene administration. When carotene supplementation was stopped, the elevated carotene levels in both plasma and RBC persisted for several mo: the elevated plasma carotene level persisted longer than the raised RBC carotene levels. .alpha.-Tocopherol and .beta.-carotene may be transported differently in the circulation and the tissue storage and mobilization of these compounds are probably different.