Epithelial dysplasia of the rabbit colon induced by degraded carrageenan

Colonic mucosal lesions, characterized by crypt abscesses and mononuclear cell infiltration, which resemble human ulcerative colitis can be induced in rabbits by short-term (7 to 8 weeks) administration of carrageenan according to our method. In this study experimental epithelial dysplasia of the colon was induced by the p.o. administration of lambda-degraded carrageenan for a much longer period of time. Fifteen rabbits, sensitized i.m. with the same substance 1 week before, were subjected to 12 or 28 months of treatment with 1% carrageenan solution in drinking water. Histological examination disclosed chiefly mild inflammatory changes of the colonic mucosa in all animals and a focal but high-grade dysplasia (nonpolypoid) involving the mucosal epithelium in three of the five animals treated for 28 months. The present observations suggested that epithelial dysplasia of the colon may be caused in association with inflammation and that the pathological condition produced by us can be a useful model of carcinoma in situ possibly resulting from inflammation.