The non-specific induction of mastocytosis in rat intestinal muscle

We examined the effects of bowel manipulation on mast-cell number and function in the rat. Mast cells were assessed histologically and by their ability to induce muscle contraction. Anaesthesia or abdominal incision did not alter mast-cell number. However, laparotomy plus brief exteriorization of jejunal segments significantly increased mast-cell number. Applying saline to the serosal surface by swab or droplet application increased mast-cell number 16- and 3-fold, respectively. Saline swabbing of jejunal segments from rats previously infected with Trichinella significantly reduced mast-cell number. Functional integrity of mast cells was illustrated by muscle contraction in vitro following compound 48/80 or antigen and inhibition of cromoglycate. Serosal application of compound 48/80 in vivo increased mast-cell number. This increase in mast-cell number by compound 48/80 or by saline was prevented by prior treatment with cromoglycate. These data suggest that mast-cell degranulation underlies the manipulation-induced mastocytosis in gut muscle.