We have developed a new experimental
ulcerative colitis model in rats. Topical pathological change of a round or a ellips shape was induced by subserosal injection of
acetic acid (20%, 0.02 ml) into the middle colon of rats. The size of the induced
ulcer could directly be measured using a caliper gauge, and the result was expressed as the
ulcer area (mm2). We determined the concentration of
leukotriene B4 (
LTB4), which is one of important clinical factors, in the
ulcer region and found that the quantity of
LTB4 was well correlated with the size of the
ulcer area. Histopathological studies of the
ulcer region demonstrated that there were some morphological similarities to the human form of
ulcerative colitis, characterized by
edema,
necrosis, inflammatory cell infiltration, crypt
abscess and granulation tissue formation. Effects of
5-aminosalicylic acid and
sodium prednisolone phosphate were investigated by intrarectal administration in this
colitis model. The predominant improvement of
colitis was obtained from both treatments in the ranges of the clinical doses of each
drug. In conclusion, we suggest that this
colitis model provides a new way for quantitative evaluation of the efficacy of new therapeutic agents for
ulcerative colitis.