Prolonged Radiation Damage in Rat Colon and Urokinase Expression in Epithelium

Although radiation therapy plays important role in the treatment of gynecological tumors, it may cause radiation injury as a late effect. Several recent reports show that urokinase such as urokinase type plasminogen activator (uPA) contributes to the repair of ulcerative lesions of the colon epithelium. We studied radiation induced enterocolitis using rat animal models. Seventy-two female Wistar rats were irradiated by a single fraction dose of 36Gy at laparotomy. Histological changes and activity of urokinase system were investigated after irradiation. Ulcers were observed in irradiated field in 12 of 19 animals (63%) even at 60th week after irradiation. Urokinase expressions were observed in the margins of active ulcer. Urokinase was thought to play important role in exacerbation of ulcer formation. Expression of uPA was also observed in submucosal glands. Ischaemic changes were not observed in irradiated colon despite sclerosing vasculitis. It is suggested that uPA played reciprocal roles in radiation induced enterocolitis: healing and aggravation of ulcer