title: Effect of D-glucose on intestinal permeability and its passive absorption in human small intestine in vivo.
abstract: BACKGROUND
  Based on studies in animals, it has been proposed that carrier-mediated D-glucose absorption markedly enhances passive permeability of the jejunal mucosa, allowing the majority of D-glucose absorption to proceed passively. In this study, we evaluated this hypothesis in the human jejunum in vivo.
  
  
  METHODS
  Using the constant perfusion, nonabsorbable marker technique, permeability of jejunal mucosa was assessed by measuring the ratio of diffusion rates of urea/L-xylose and mannitol/L-xylose. Passive D-glucose absorption was quantitated using L-glucose and mannitol as probes for D-glucose.
  
  
  RESULTS
  Addition of D-glucose to perfused solutions did not change the diffusion ratios, indicating that D-glucose has no effect on the size of channels for passive diffusion across the jejunal mucosa. The fraction of total D-glucose absorption that could be attributed to a passive mechanism averaged 5%. In the human ileum in vivo, we detected no evidence of passive D-glucose absorption.
  
  
  CONCLUSIONS
  Carrier-mediated D-glucose absorption does not increase passive permeability of human jejunal mucosa to solutes with molecular radii between 2.6 and 4.0 A. The amount of D-glucose absorbed passively from the human jejunum is trivial compared with the overwhelmingly dominant mechanism, carrier-mediated transport. Our results do not support the concept that sodium-dependent nutrient transport increases tight junction permeability.
authors.affiliation: Department of Internal Medicine, Baylor University Medical Center, Dallas, Texas.
authors.forename: K D
authors.initials: KD
authors.lastname: Fine
authors.forename: C A
authors.initials: CA
authors.lastname: Santa Ana
authors.forename: J L
authors.initials: JL
authors.lastname: Porter
authors.forename: J S
authors.initials: JS
authors.lastname: Fordtran
mesh_terms: D005947:Glucose / Q000494:pharmacology*; D006801:Humans; D007082:Ileum / Q000378:metabolism* / Q000648:ultrastructure; D007408:Intestinal Absorption / Q000187:drug effects* / Q000502:physiology; D007413:Intestinal Mucosa / Q000378:metabolism / Q000648:ultrastructure; D007536:Isomerism; D007583:Jejunum / Q000378:metabolism* / Q000648:ultrastructure; D008353:Mannitol / Q000493:pharmacokinetics; D014508:Urea / Q000493:pharmacokinetics; D014994:Xylose / Q000493:pharmacokinetics
chemical_list: D008353:Mannitol; D014508:Urea; D014994:Xylose; D005947:Glucose