TRANSPORT OF DEUTERIUM-LABELED TOCOPHEROLS DURING PREGNANCY

With use of deuterium-labeled isotopes of RRR- and all-rac-alpha-tocop heryl acetate, the transport of vitamin E in pregnancy was evaluated t o determine whether the placenta discriminates between these compounds . Fifteen pregnant subjects were recruited 5 d before delivery to rece ive 15, 30, 75, 150, or 300 mg vitamin E/d in capsules containing d3-R RR-alpha-tocopheryl acetate and d6-all-rac-alpha-tocopheryl acetate (1 :1, by wt). Maternal blood was obtained before dosing, at hospital adm ission, and at parturition. Cord blood samples were obtained at partur ition. Deuterium-labeled and unlabeled tocopherol contents were determ ined by gas chromatography-mass spectrometry in plasma and lipoprotein s (chylomicrons, VLDL, LDL, and HDL). Maternal plasma and lipoproteins obtained at delivery had higher concentrations of d3-RRR-alpha-tocoph erol than d6-all-rac-alpha-tocopherol regardless of the vitamin E dose administered (P < 0.05). Cord plasma at delivery also had higher conc entrations of d3-RRR-alpha-tocopherol than d6-all-rac-alpha-tocopherol in plasma irrespective of the dose administered (P < 0.05). In lipopr oteins isolated from cord blood, tocopherol concentrations were greate st in the HDL fraction (P < 0.05), whereas in maternal blood they were greatest in the LDL fraction (P < 0.05). We conclude that the placent al-fetal unit, the fetal liver, or both further discriminate between R RR- and all-rac-alpha-tocopherol.