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Updated: Jun 28, 2026

Functional Assessment of Intestinal Tight Junction Barrier and Ion Permeability in Native Tissue by Ussing Chamber Technique
Published on: May 26, 2021
Na+ absorption defends from paracellular back-leakage by claudin-8 upregulation
Salah Amasheh1, Susanne Milatz, Susanne M Krug
1Institute of Clinical Physiology, Charité, Campus Benjamin Franklin, Hindenburgdamm 30, 12200 Berlin, Germany.
Abstract:
In distal colon, the limiting factor for Na(+) absorption is represented by the epithelial sodium channel (ENaC). During absorption, high transepithelial Na(+) gradients are observed. In human colon and in HT-29/B6-GR cells, we investigated whether Na(+) back-leakage is prevented by paracellular sealing. Tissues and cells were incubated with corticosteroids. Barrier properties were analyzed in electrophysiological experiments. Subsequently, analysis of ENaC and tight junction protein expression, localization, and regulation was performed. In colon, nanomolar aldosterone induced sodium absorption via ENaC. Concomitantly, paracellular (22)Na(+) permeability was reduced by half and claudin-8 within the tight junction complex was nearly doubled. Real-time PCR validated an increase of claudin-8 transcripts. Two-path impedance spectroscopy following ENaC induction in HT-29/B6-GR revealed a specific increase of paracellular resistance. These results represent an important physiological implication: Na(+) absorption is paralleled by claudin-8-mediated sealing of the paracellular barrier to prevent Na(+) back-leakage, supporting steep Na(+) gradients in distal colon.
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