Gastroenterology

Gastroenterology

Volume 119, Issue 4, October 2000, Pages 1029-1036
Gastroenterology

Alimentary Tract
Permeability of the rat small intestinal epithelium along the villus-crypt axis: Effects of glucose transport,☆☆

https://doi.org/10.1053/gast.2000.18148Get rights and content

Abstract

Background & Aims: The aim of this study was to elucidate the permeability characteristics of the epithelium along the villus-crypt axis and investigate the effect of glucose transport on these characteristics along this axis. Methods: The disappearance rates of 14C-mannitol and 51Cr-EDTA or 3H-inulin were determined as clearance (Clx) from a recirculating perfusion system of the jejunal lumen in anesthetized rats. Net fluid transport was varied over a large range by exchanging mannitol with glucose in the perfusate solution and by inhibition of nervously mediated secretory processes with hexamethonium. The perfusion rate was 0.5 or 0.2 mL/min. Results: ClMan enhanced significantly with increasing net fluid transport (secretion 8.50 ± 1.88, to absorption 16.72 ± 1.75 μL · min−1 · g−1) and with glucose perfusates. ClCr-EDTA was constant irrespective of net fluid transport and was reduced to insignificant values at a perfusion rate of 0.2 mL/min. ClIn was not different from zero. Conclusions: The absorbing apical part of the villus contains small pores (radius, <6 Å) allowing passive transport via solvent drag of, e.g., monosaccharides, whereas the pores in the crypts are large (50–60 Å) and inaccessible to the luminal content. The basal part of the villus contains medium-sized pores (10–15 Å) through which no solvent drag occurs. Active glucose transport in the rat mainly increases the number of small pores accessible for passive transport, whereas the size of these pores seems to stay constant.

GASTROENTEROLOGY 2000;119:1029-1036

Section snippets

Operative procedures

The experiments were performed on male Sprague–Dawley rats (Alab, Stockholm, Sweden) weighing 250–450 g. The animals were kept under standardized environmental conditions (22°C, 60% humidity, artificial light from 6 AM to 6 PM) in the animal quarters for at least 7 days before the experiment. The animals were deprived of food 12 hours before the experiments with full access to water. Anesthesia was induced with pentobarbitone (60 mg/kg, intraperitoneally). A tracheal cannula was inserted to

Tissue content of 51Cr-EDTA and 14C-mannitol

In 4 experiments, the tissue content of 51Cr-EDTA and 14C-mannitol was determined in an intestinal segment after a perfusion period of 4 hours with the Krebs–Henseleit solution containing glucose. A nonperfused control segment was also taken for analysis of probe content. The amount of 51Cr-EDTA and 14C-mannitol in the tissue of the test segment corresponded to 1.4% of the total amount absorbed for both isotopes and to 0.65% and 0.85% in the control tissue, respectively. The autoradiographs

Discussion

The method used in this study gave a significant and reproducible clearance of mannitol and Cr-EDTA but did not detect a significant clearance of inulin, independent of the presence of mannitol or glucose in the perfusate. The clearance values were not erroneously affected by markers left in the intestinal lumen at the end of the perfusion period, e.g., by adhering to the mucous layer. This is shown by the autoradiographic experiments and by the observation that the ClCr-EDTA in one

References (35)

  • D. Hollander

    The intestinal permeability barrier. A hypothesis as to its regulation and involvement in Crohn's disease

    Scand J Gastroenterol

    (1992)
  • TY Ma et al.

    Is the small intestinal epithelium truly “tight” to inulin permeation?

    Am J Physiol

    (1991)
  • JR Pappenheimer et al.

    Contribution of solvent drag through intercellular junctions to absorption of nutrients by the small intestine

    J Membr Biol

    (1987)
  • DC Sadowski et al.

    Luminal nutrients alter tight-junction permeability in the rat jejunum: an in vivo perfusion model

    Can J Physiol Pharmacol

    (1993)
  • A Sjöqvist et al.

    Transcellular fluid secretion induced by cholera toxin and vasoactive intestinal polypeptide in the small intestine of the rat

    Acta Physiol Scand

    (1993)
  • K Loeschke et al.

    Osmotic water flow pathway across necturus gallbladder: role of the tight junction

    Am J Physiol

    (1994)
  • D Hollander et al.

    Importance of “probe” molecular geometry in determining intestinal permeability

    Can J Gastroenterol

    (1988)
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    Supported by Swedish Medical Research Council (2855) and Åke Wiberg Foundation.

    ☆☆

    Address requests for reprints to: Mats Jodal, M.D., Department of Physiology, Box 432, S- 405 30 Göteborg, Sweden. e-mail: [email protected]; fax: (46) 31-773-3512.

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