Uptake of intact TPGS (d-alpha-tocopheryl polyethylene glycol 1000 succinate) a water-miscible form of vitamin E by human cells in vitro.
The mechanism by which TPGS (alpha-tocopheryl succinate esterified to polyethylene glycol 1000 [PEG 1000]) delivers tocopherol (vitamin E) was studied in human fibroblasts and erythrocytes and a human intestinal cell line, Caco-2. The total cellular tocopherol content of saponified samples of fibroblasts or Caco-2 incubated for 4 h with TPGS (4 mumol/L) increased 10-fold without an increase in the free tocopherol content of nonsaponified samples. A 24-h incubation resulted in a free tocopherol content of approximately 20%, suggesting that intracellular hydrolysis of ester bonds had occurred. The increase in total tocopherol content after a 4-h incubation with TPGS was temperature dependent; no change was measurable at 4 degrees C. Addition of metabolic inhibitors during incubation with TPGS at 37 degrees C did not prevent the increase. [14C]TPGS (synthesized from [14C]PEG 1000) was taken up by Caco-2 cells but [14C]PEG 1000 was not. The intracellular total tocopherol (pmol) equaled the [14C]TPGS (pmol), unequivocally demonstrating uptake of the intact TPGS molecule.
Department of Medicine, New York University School of Medicine, NY 10016.
M G
MG
Traber
C A
CA
Thellman
M J
MJ
Rindler
H J
HJ
Kayden
D002250:Carbon Radioisotopes; D002460:Cell Line; D002779:Cholestasis / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism*; D006801:Humans; D006868:Hydrolysis; D007413:Intestinal Mucosa / Q000378:metabolism*; D007700:Kinetics; D011092:Polyethylene Glycols / Q000378:metabolism; D012995:Solubility; D013696:Temperature; D024505:Tocopherols; D014810:Vitamin E / Q000031:analogs & derivatives* / Q000378:metabolism; D014867:Water
D002250:Carbon Radioisotopes; D014867:Water; D014810:Vitamin E; D011092:Polyethylene Glycols; C014225:tocophersolan; D024505:Tocopherols