Therapeutic effect of methyl 5-aminosalicylate on experimental ulcerative colitis in rabbits

Using the improved Kirsner model of ulcerative colitis in rabbits, we found that the therapeutic effect of methyl 5-amino salicylate hydrochloride (M-5-AS) was similar to that of sulfasalazine (salicylazosulfapyridine, SZ). The length of pathological damage and the range of diffuse ulcers were decreased in comparison with the control group (P less than 0.01, 0.05). Microscopically, tissue repairing at the regions of ulcers and proliferation in serolemma were noted, and the edema in muscular mesenchyme was less evident in the treated rabbits. M-5-AS completely inhibited the spontaneous contraction of rat stomach fundus strips and colon. The IC50 of the resting tone of the 2 tissues were 1.30 +/- 0.39 and 0.72 +/- 0.25 mmol/L, respectively. In addition, M-5-AS antagonized the contraction induced by human fresh semen. The results suggest that the therapeutic mechanism is related to the antagonism of prostaglandins in the inflammatory regions.