Environmental stress causes mast cell degranulation, endothelial and epithelial changes, and edema in the rat intestinal mucosa

Objective: Mental stress has been shown to produce intestinal disease, but the effects of a mild environmental stress on intestinal physiology have not been elucidated. This study was performed to determine the effects of environmental stress on the ultrastructure of the intestinal mucosa, using the rat as an experimental model. Methods: One group of rats (group A, n = 3) was examined immediately upon arrival at the animal care facility. Groups B (n = 6) and C (n = 6) were housed in rooms with high and low personnel activity, respectively, for up to 4 wk. Group D (n = 8) was housed in the high activity room for 3 to 4 wk followed by 1, 2, or 3 in the low activity room. Results: Rats in group B had the greatest number of degranulated intestinal mucosal mast cells, and activated goblet cells. Intestinal villi were edematous and epithelial cells were detaching from the basement membrane at villus tips. Changes were observed in capillary endothelial ultrastructure. In group B there were greater numbers of vesicles and multilamellar fenestral diaphragms compared to group C. Rats in groups A and C had the lowest numbers of degranulated mast cells and activated goblet cells. Intestinal villi showed normal ultrastructure. Group D was in a recovery phase and the condition of the intestinal mucosa was improved relative to group B, but the number of degranulated mast cells was not significantly reduced. Conclusions: This study demonstrates that environmentally induced stress causes pathological changes in the rat intestinal mucosa that compromise the epithelial-endothelial exchange barrier. These results emphasize the importance of closely monitoring the environment of experimental animals and provide evidence to stimulate further research into the mechanisms linking mental stress to gastrointestinal dysfunction in humans.