title: Pathway of oral absorption of heparin with sodium N-[8-(2-hydroxybenzoyl)amino] caprylate.
abstract: OBJECTIVE
  The oral bioavailability of heparin is negligible. Recent studies, however, have shown that sodium N-[8-(2-hydroxybenzoyl) amino]caprylate (SNAC) and other N-acylated amino acids enable oral heparin absorption. To investigate the mechanism by which heparin crosses the intestinal epithelium in the presence of SNAC, we have used fluorescence microscopy to follow the transport of heparin across Caco-2 cell monolayers.
  
  
  METHODS
  The experiments were carried out on Caco-2 monolayers and Caco-2 cells grown to confluence on culture dishes, using different concentrations of SNAC. The localization of fluorescently labeled heparin was determined using epi-fluorescence and confocal microscopy. DNA dyes were used to determine the effect of SNAC on the plasma membrane integrity. F-actin was labeled with fluorescent phalloidin to investigate the stability of perijunctional actin rings in the presence of SNAC.
  
  
  RESULTS
  Heparin was detected in the cytoplasm only after incubation of the cells with heparin and SNAC. No DNA staining was observed in cells incubated with a DNA dye in the presence of SNAC concentrations at which heparin transport occurred. In addition, no signs of actin redistribution or perijunctional ring disbandment were observed during the transport of heparin.
  
  
  CONCLUSIONS
  The results indicate that SNAC enables heparin transport across Caco-2 monolayers via the transcellular pathway. Heparin transport in the presence of SNAC is selective and does not involve permeabilization of the plasma membrane or tight junction disruption.
authors.affiliation: Emisphere Technologies, Inc., Tarrytown, New York 10591, USA.
authors.forename: Dmitry
authors.initials: D
authors.lastname: Malkov
authors.forename: Huai-Zhen
authors.initials: HZ
authors.lastname: Wang
authors.forename: Steven
authors.initials: S
authors.lastname: Dinh
authors.forename: Isabel
authors.initials: I
authors.lastname: Gomez-Orellana
mesh_terms: D000284:Administration, Oral; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D018938:Caco-2 Cells; D002210:Caprylates / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006493:Heparin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D006801:Humans
chemical_list: D002210:Caprylates; C111140:N-(8-(2-hydroxybenzoyl)amino)caprylate; D006493:Heparin