Involvement of DNA fragmentation of enterocytes in mucosal injury to a mouse jejunum incubated in ussing chambers.

A mouse jejunum, when incubated in vitro in Ussing chambers, was found to exhibit morphological deterioration of the villi with denudation of the epithelia (J Nutr Sci Vitaminol, 51: 406, 2005). Our study examined the involvement of apoptosis in an intestinal injury model by a DNA ladder assay and terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay. Electrophoresis of mucosal DNA revealed ladders, indicating the occurrence of DNA fragmentation.

The electrophysiological properties of the mucosal barrier in the injured mouse jejunum in Ussing chambers.

We previously suggested in the in vitro mouse jejunum that when the primary epithelial barrier on the villi was largely disabled, a secondary mucosal barrier substitutes for the primary one. This study showed that the mucosal Ca(2+) removal did not further deteriorate the histology but increased transmural conductance and lucifer yellow flux, and decreased forskolin-induced potential difference. It is suggested that in this injury model the postulated secondary barrier is Ca(2+)-dependent and likely to be present on or immediately beneath the mucosal surface.

In vitro diffusion barriers of the mouse jejunum in Ussing chambers.

Epithelial cells and their intercellular junctions play a primary role in the intestinal mucosal diffusion barrier to the invasion of noxious agents. Our previous study has shown that the mouse jejunum, when incubated in Ussing chambers for 4 h, exhibited morphological deterioration of the villi with denudation of the epithelia while it retained cAMP-induced potential difference (PD), suggesting that some subepithelial tissues had taken part in the barrier functions when the primary epithelial barrier on the villous surface was broken. To further characterize the barrier function of the jejunum in Ussing chambers, we measured the unidirectional lucifer yellow flux (J(LY)), which represents the permeation of a medium-sized anion, the transmural electrical conductance (G(t)), which reflects the permeation of electrolytes, mainly NaCl, and forskolin-induced PD.