Colonic mucin release in response to immobilization stress is mast cell dependent

We recently reported that immobilization stress increased colonic motility, mucin, and prostaglandin E₂ (PGE₂) release and mucosal mast cell degranulation in rat colon [Proc. Natl. Aced. Sci. USA 93: 12611-12615, 1996; Am. J. Physiol. 271 (Gastrointest. Liver Physiol. 34): G884-G892, 1996]. To directly assess the contribution of mast cells, we compared colonic responses to stress in mast cell-deficient Kit(W)/Kit(W-v) and normal (+/+) mice. Mucin and PGE₂ release were measured in colonic explants cultured from Kit(W)/Kit(W-v) and (+/+) mice 30 min after immobilization stress. We found that stress stimulated colonic mucin release (1.8-fold), goblet cell depletion (3-fold), and PGE₂ (2.3-fold) release in (+/+) but not mast cell- deficient Kit(W)/Kit(W-v) mice. However, mast cell-deficient mice that had their mast cell population reconstituted by injection of bone marrow-derived mast cells from (+/+) mice had colonic responses to stress similar to those of normal (+/+) mice. In contrast, colonic transit changes in response to stress, estimated by fecal output, were similar between Kit(W)/Kit(W-v) and normal (+/+) mice. We conclude that mast cells regulate colonic mucin and PGE₂ release but not colonic transit changes in response to immobilization stress.