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Acidosis induces hyperpermeability in Caco-2BBe cultured intestinal epithelial monolayers
M J Menconi1, A L Salzman, N Unno
1Department of Surgery, Beth Israel Deaconess Medical Center, Boston, Massachusetts, USA.
The American Journal of Physiology
|May 1, 1997
Summary
Acidosis reversibly increases intestinal permeability to hydrophilic macromolecules by affecting both paracellular and transcellular pathways. This process, observed in human intestinal cells, also leads to cellular ATP depletion.
Area of Science:
- Gastroenterology
- Cell Biology
- Physiology
Background:
- Ileal mucosal acidosis in pigs was previously shown to increase intestinal permeability to hydrophilic macromolecules.
- The underlying mechanisms of this phenomenon require further exploration.
Purpose of the Study:
- To investigate the effect of acidic pH on the permeability characteristics of cultured Caco-2BBe human intestinal epithelial cells.
- To elucidate the mechanisms by which acidosis influences intestinal permeability.
Main Methods:
- Cultured Caco-2BBe cells were grown as monolayers and exposed to acidic conditions (pH 5.43) or hypercarbic conditions.
- Permeability was assessed by measuring the flux of fluorescein disulfonic acid (FS), fluorescein isothiocyanate-labeled dextran (FD4), and mannitol.
- Cellular integrity was evaluated by lactate dehydrogenase release and calcein-acetoxymethyl ester staining. Ultrastructural analyses and fluorescence confocal microscopy were employed.
Main Results:
- Acidic pH significantly increased permeability to FS, FD4, and mannitol in a time- and pH-dependent manner.
- Plasma membrane injury was indicated by increased lactate dehydrogenase release and decreased calcein staining, without increased cell death.
- Ultrastructural analysis showed increased paracellular trafficking, while microscopy suggested increased transcellular permeation and decreased cellular ATP levels.
Conclusions:
- Acidosis increases both paracellular and transcellular permeability to hydrophilic macromolecules in intestinal epithelial cells.
- The observed increase in permeability is associated with plasma membrane injury and ATP depletion.
- These findings contribute to understanding the impact of acidosis on intestinal barrier function.