ENZYME CHANGES IN REMODELING EPITHELIAL-CELLS - A HISTOCHEMICAL-STUDYOF THE RAT JEJUNUM IN-VIVO DURING AND FOLLOWING EXPOSURE TO DEOXYCHOLIC-ACID

Loops of rat jejunum were exposed in vivo to different concentrations of deoxycholic acid (DOC; 0, 2.5, 5, 10 and 20 mM). Following a 30 min exposure period, DOC was washed out of the loops and the intestines w ere allowed to recover for 15 or 150 min. Frozen tissue for enzyme his tochemistry was collected during exposure and following the recovery p eriods. As shown previously, exposure to DOC caused a dose-dependent l oss of epithelial cells at the villous tips and denudation of the lami na propria. Flattened epithelial cells bordering the denuded areas wer e, however, responsible for a rapid restoration of epithelial continui ty, which was completed within 15 min. In the present study, these fla ttened cells showed normal reactivity for non-specific esterase and su ccinate dehydrogenase. In contrast, following a prolonged recovery per iod (150 min), a subpopulation of enterocytes at the villous tips that otherwise appeared normal showed decreased reactivity for brush borde r enzymes and non-specific esterase, and a positive reaction for mucin . A shutdown in the synthesis of cytoplasmic enzymes and redistributio n of cell surface enzymes could be responsible for these late occuring enzyme changes, that were consistently observed after 150 min of reco very from DOC at 20 mM. Alternatively, retention of goblet cells and/o r a modification in enzyme synthesis may explain the presence of mucin that was demonstrated in the epithelial cells which had low enzyme re activity.