title: Protection by vitamin C of loss of vitamin E in cultured rat hepatocytes.
abstract: Results from in vivo studies of the capacity of vitamin C to spare and/or recycle vitamin E are equivocal. While some in vitro and membrane models reveal an interaction between vitamins C and E, the characterization of this relationship in biologically relevant systems is lacking. Thus, we investigated this relationship using hepatocytes isolated from 3- to 6-month-old male Sprague-Dawley rats. Cells were incubated for 18-20 h in medium supplemented with 0.1-4 mM ascorbic acid. The loss of alpha-tocopherol and the formation of its primary oxidized metabolite, alpha-tocopherolquinone, was determined by HPLC. Levels of alpha-tocopherol in hepatocytes incubated without ascorbic acid declined from 390 to 35 pmol/mg protein; hepatocyte ascorbic acid levels declined from 9 to 0.5 nmol/mg protein. alpha-Tocopherolquinone was undetectable in freshly isolated hepatocytes but following incubation in ascorbate-free medium reached 10 pmol/mg protein. The formation of alpha-tocopherolquinone was not detected in hepatocytes incubated with ascorbic acid. Dehydroascorbic acid (DHA) levels represented 10-20% of the total ascorbate content in freshly isolated hepatocytes but after 3 h incubation the proportion of DHA increased to 50%; after 18-20 h incubation DHA was undetectable. Hepatocytes incubated with 1.0, 2.0, 2.5, or 4.0 mM ascorbic acid lost significantly less alpha-tocopherol (62, 69, 67, and 56%, respectively) than unsupplemented controls (90%). Twelve percent of the alpha-tocopherol lost from hepatocytes during incubation was detected in the medium of cells incubated with ascorbic acid, but vitamin E was undetectable in the medium of cells incubated without ascorbic acid. These results demonstrate an interaction between vitamins C and E in cell culture and are not inconsistent with a potential recycling of oxidized alpha-tocopherol by ascorbic acid.
authors.affiliation: Antioxidants Research Laboratory, Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts, 02111, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Halpner
authors.forename: G J
authors.initials: GJ
authors.lastname: Handelman
authors.forename: J M
authors.initials: JM
authors.lastname: Harris
authors.forename: C A
authors.initials: CA
authors.lastname: Belmont
authors.forename: J B
authors.initials: JB
authors.lastname: Blumberg
mesh_terms: D000818:Animals; D001205:Ascorbic Acid / Q000502:physiology*; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D004305:Dose-Response Relationship, Drug; D005978:Glutathione / Q000378:metabolism; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014810:Vitamin E / Q000031:analogs & derivatives / Q000096:biosynthesis / Q000378:metabolism*
chemical_list: D017077:Culture Media, Conditioned; D014810:Vitamin E; C002421:tocopherylquinone; D005978:Glutathione; D001205:Ascorbic Acid