Ascorbic acid transport and distribution in human B lymphocytes.
Ascorbic acid (vitamin C) transport was investigated in human B lymphocytes. The vitamin was transported by two components. The first was a high-affinity activity with an apparent Km of 7-10 microM and Vmax of 0.14 mM/h (3.11 x 10(-4) mumol x h-1 x mg protein-1). The activity was concentration and temperature dependent, saturable, and inhibited by carbonylcyanide-p-trifluoromethoxyphenylhydrazone and ouabain and generated ascorbic acid accumulation against a concentration gradient. Kinetics for the second component were indeterminate because ascorbate was not accumulated against a concentration gradient. Subcellular fractionation revealed that intracellular ascorbic acid in human B lymphocytes was > 90% localized to the cytosol and not protein bound. Kinetic parameters of high-affinity ascorbic acid transport could operate effectively with plasma concentrations normally found in humans.
Bergsten
P
P
Laboratory of Cell Biology and Genetics, National Institute of Diabetes, Digestive, and Kidney Diseases, National Institutes of Health, Bethesda, Maryland 20892.
Yu
R
R
Kehrl
J
J
Levine
M
M
D001205:Ascorbic Acid / Q000378:metabolism*; D001402:B-Lymphocytes / Q000378:metabolism*; D001692:Biological Transport; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D002451:Cell Compartmentation; D002478:Cells, Cultured; D003470:Culture Media; D006801:Humans; D010042:Ouabain / Q000494:pharmacology; D014066:Palatine Tonsil / Q000378:metabolism
D003470:Culture Media; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D010042:Ouabain; D001205:Ascorbic Acid