Physiological assessment of epithelial function in damaged rat colon

To assess colonic damage quantitatively by electrophysiological parameters such as membrane potential difference, short circuit current and transepithelial resistance, and by colonic membrane permeability (permeation clearance) of FITC-labelled dextran 4000.

For experimental colitis models of rats, trinitrobenzene sulphonic acid-, acetic acid-, and dextran sulphate sodium-induced models were employed. The Ussing-type chamber was used for determination of the electrophysiological parameters and permeation clearance of FITC-labelled dextran 4000.

Reductions of all the above electrophysiological parameters were observed in trinitrobenzene sulphonic acid- and acetic acid-induced models. No good correlation between the reduction in the parameters and the intestinal damage score was found in any of the models. This shows that damage scores do not necessarily reflect precise changes in physiological epithelial function. In contrast, the electrophysiological parameters were well correlated with membrane permeability. The reduction in transepithelial resistance, i.e. reduction in barrier function, was supported by an increase in permeation clearance of FITC-labelled dextran 4000 and the plasma appearance of endotoxin in the trinitrobenzene sulphonic acid-induced model. Through the recovery of transepithelial resistance and permeation clearance of FITC-labelled dextran 4000 to control values in the acetic acid-induced model, automatic recovery of the model to normal occurred.

Examination of the electrophysiological parameters and permeation clearance of FITC-labelled dextran 4000 can provide a useful method of assessment of epithelial damage.