title: Paracellular transport of avidin saturated or not with biotinylated cobalamin through Caco-2 cell epithelium monolayer.
abstract: BACKGROUND
  The cationic charge of molecules may promote their uptake across epithelia, which are rich in brush border anionic sites. The transport of unsaturated avidin and avidin saturated with a biotinylated compound was investigated across Caco-2 adenocarcinoma cell with fetal enterocyte phenotype.
  
  
  METHODS
  The unsaturated avidin and avidin saturated with either biotin or a biotinyl-cobalamin conjugate (biotinyl-Cbl) were iodinated to follow their transport through the cell monolayer. Their apparent permeability coefficient (Papp) and transepithelial pathway were determined and compared to those for control radiolabeled markers [3H]-mannitol, [125I]-beta-lactoglobulin and [57Co]-cobalamin/intrinsic factor (Cbl/IF).
  
  
  RESULTS
  The Papp of [125I]-avidin estimated at 2.8 x 10(-7) +/- 0.08 cm/s was close to that for mannitol that uses paracellular pathway. The binding of biotin or biotin conjugate to avidin enhanced its tetrameric conformation. The Papp for [125I]-avidin/biotin and [125I]- avidin/biotinyl-Cbl were respectively increased by 2-fold, compared to that for [125I]-avidin and 4-fold, compared to that for [125I]-beta-lactoglobulin and [54Co]-Cbl/IF. The protein was not accumulated in the cell and was found in intact form in the basolateral side, after its transport across the monolayer. Chloroquine (0.66 micromol/ml) did not significantly decrease the Papp for [125I]-avidin/biotinyl-Cbl. Conversely it decreased by 80% the Papp for Cbl/IF, that uses transepithelial pathway.
  
  
  CONCLUSIONS
  Avidin (either saturated or not with biotin and biotinyl-Cbl) was able to cross the monolayer of Caco-2 cell line through a paracellular pathway. This study pointed out the interest for using this protein as a shuttle for increasing the transport rate of biotinylated compounds through fetal epithelial barriers.
authors.affiliation: Laboratoire de Pathologie Cellulaire et Moleculaire en Nutrition-EMI INSERM 0014-URM IFREMER 20, Faculté de Médecine, Universite de Nancy.
authors.forename: M
authors.initials: M
authors.lastname: Guy
authors.forename: L
authors.initials: L
authors.lastname: Pons
authors.forename: F
authors.initials: F
authors.lastname: Namour
authors.forename: M
authors.initials: M
authors.lastname: de Nonancourt
authors.forename: J C
authors.initials: JC
authors.lastname: Michalski
authors.forename: R
authors.initials: R
authors.lastname: Hatier
authors.forename: J L
authors.initials: JL
authors.lastname: Guéant
mesh_terms: D001360:Avidin / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D019921:Biotinylation; D018938:Caco-2 Cells; D002738:Chloroquine / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism*; D007437:Intrinsic Factor / Q000378:metabolism; D007782:Lactoglobulins / Q000378:metabolism; D008353:Mannitol / Q000378:metabolism; D014805:Vitamin B 12 / Q000378:metabolism*
chemical_list: D007782:Lactoglobulins; D001360:Avidin; D008353:Mannitol; D002738:Chloroquine; D007437:Intrinsic Factor; D004492:Edetic Acid; D014805:Vitamin B 12