title: Influence of sources of dietary vitamin E on the maternal transfer of alpha-tocopherol to fetal and neonatal guinea pigs as determined by a stable isotopic technique.
abstract: The accepted biological potencies of vitamin E (United States Phamacopeia, 1985) for 1 mg all-rac-alpha-tocopheryl acetate (synthetic form) is 1.00 IU and that of 1 mg (RRR)-alpha-tocopheryl acetate (natural form) is 1.36 IU. In the present study, a stable isotopic (2H) technique was employed to evaluate the bioavailability of natural v. synthetic forms of vitamin E and to determine whether the potency of the forms is the stated relationship of 1.36:1.00 (RRR)-alpha-tocopheryl acetate:all-rac-alpha-tocopheryl acetate. Sixty female in-bred guinea pigs received either 40 or 80 mg vitamin E/kg diet with equal levels of (RRR)-alpha-tocopheryl acetate and all-rac-alpha-tocopheryl acetate throughout gestation and lactation. At late-term pregnancy (day 50 or 60) and during early lactation, dams and their corresponding fetuses or neonates were killed and various tissues collected for subsequent alpha-tocopherol analysis. Vitamin E analysis of fetal and neonatal tissues indicated a substantial transfer of 2H-labelled alpha-tocopherol across the placenta and through the mammary gland. Total alpha-tocopherol concentrations were significantly influenced by tissue type and dose level, but not by stage of gestation or lactation. The relative bioavailability (d3:d6) across fetal and neonatal tissues was on average 1.81:1.00, with a range from 1.62:1.00 to 2.01:1.00. Maternal tissues had a mean ratio of 1.77:1.00. A higher relative bioavailability (P<or=0.05) was observed with natural compared with synthetic alpha-tocopherol as shown by a higher d3:d6 ratio in all tissues examined. Vitamin E was highest in colostrum on day 2 then declined through to day 5. Results from this present experiment further question the accepted biological potencies of natural:synthetic alpha-tocopheryl acetate of 1.36:1.00.
authors.affiliation: Nutrition Research Division, Health Products and Food Branch, Health Canada, Banting Research Center (PL 2203C), Tunneys Pasture, Ottawa, Ontario, Canada. Nick_Hidiroglou@hc-sc.gc.ca
authors.forename: N
authors.initials: N
authors.lastname: Hidiroglou
authors.forename: R
authors.initials: R
authors.lastname: Madere
authors.forename: L R
authors.initials: LR
authors.lastname: McDowell
authors.forename: P L
authors.initials: PL
authors.lastname: Toutain
mesh_terms: D000818:Animals; D017849:Animals, Inbred Strains; D000831:Animals, Newborn / Q000378:metabolism*; D001682:Biological Availability; D004305:Dose-Response Relationship, Drug; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006168:Guinea Pigs; D007553:Isotope Labeling; D007774:Lactation; D008321:Mammary Glands, Animal / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D009752:Nutritional Status; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D014810:Vitamin E / Q000008:administration & dosage / Q000378:metabolism*; D024502:alpha-Tocopherol / Q000378:metabolism
chemical_list: D014810:Vitamin E; D024502:alpha-Tocopherol