DISCRIMINATION BETWEEN RRR-RACEMIC-ALPHA-TOCOPHEROL AND ALL-RACEMIC-ALPHA-TOCOPHEROL LABELED WITH DEUTERIUM BY PATIENTS WITH ABETALIPOPROTEINEMIA

The ability to discriminate between stereoisomers of alpha-tocopherol was studied in five patients with abetalipoproteinemia (ABL) because a n impairment in secretion of apolipoprotein B-containing lipoproteins might impede the normally enhanced plasma transport of RRR-alpha-tocop herol. An oral dose containing 3.7 g of each 2R,4'R,8'R-alpha-[5-(CH3) -H-2,]tocopheryl acetate (d(3)RRR-alpha-tocopheryl acetate) and 2RS,4' RS,8'RS-alpha-[5,7-((CH3)-H-2)(2)]tocopheryl acetate (d(6)all rac-alph a-tocopheryl acetate) was administered, then the labeled and unlabeled alpha-tocopherol contents of plasma and red blood cells from multiple blood samples obtained at selected times up to 72 h following the dos e were quantitated. ABL plasma contained about 1%-10% of the d(3)-RRR- alpha-tocopherol concentrations of normal subjects given only 150 mg o f each isotope. Three of the patients discriminated between forms of a lpha-tocopherol with ratios of RRR-/allrac-alpha-tocopherol greater th an or equal to 1.8, similar to normals. These data suggest that the he patic tocopherol binding protein is present and functional in ABL pati ents. Although two of the patients did not discriminate between stereo isomers of alpha-tocopherol, it is likely that this resulted from near ly a complete block in very low density lipoprotein (VLDL) secretion. Thus, the ability of ABL patients to absorb and transport orally admin istered vitamin E is markedly impaired and variable among patients.