COLONIC MUCIN RELEASE IN RESPONSE TO IMMOBILIZATION STRESS IS MAST-CELL DEPENDENT

We recently reported that immobilization stress increased colonic moti lity, mucin, and prostaglandin E-2 (PGE(2)) release and mucosal mast c ell degranulation in rat colon [Proc. Natl. Acad. Sci. USA 93: 12611-1 2615, 1996; Am. J. Physiol. 271 (Gastrointest. Liver Physiol. 34): G88 4-G892, 1996]. To directly assess the contribution of mast cells, we c ompared colonic responses to stress in mast cell-deficient Kit(W)/Kit( W-v) and normal (+/+) mice. Mucin and PGE(2) release were measured in colonic explants cultured from Kit(W)/Kit(W-v) and (+/+) mice 30 min a fter immobilization stress. We found that stress stimulated colonic mu cin release (1.8-fold), goblet cell depletion (3-fold), and PGE(2) (2. 3-fold) release in (+/+) but not mast cell-deficient Kit(W)/Kit(W-v) m ice. However, mast cell-deficient mice that had their mast cell popula tion 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 stres s, estimated by fecal output, were similar between Kit(W)/Kit(W-v) and normal (+/+) mice. We conclude that mast cells regulate colonic mucin and PGE(2) release but not colonic transit changes in responsetom imm unobilization stress.