Characteristics of immune-complex-induced chronic experimental colitis in rats with a therapeutic effect of sulphasalazine.

Experimental colitis was induced in rats by topical irritation of the colonic mucosa with 1 ml of 1% formalin followed by intravenous injection of 0.5 ml soluble immune complexes (IC) made in vitro in antigen excess and having characterized precipitation and complement activation profiles. The rats had been preimmunized with Escherichia coli O14:K7:H- to produce antibodies cross-reactive with colonic mucosa, thus aggravating the colitis to chronicity. Histologic evaluation of inflammation in the colon was performed on days 6, 12, and 18 by determining the number of phagocytic cells. The colitis was inhibited by sulphasalazine therapy given daily, 125.5 mumols (50 mg)/kg body weight, starting on the day when the inflammation was produced with IC and formalin. Sulphasalazine therapy significantly (p less than 0.05) decreased the number of phagocytic cells in the mucosa on days 12 and 18 but not on day 6. The results may give a clue to the beneficial pharmacologic effects of sulphasalazine in the treatment of ulcerative colitis.