RADIATION EFFECTS IN THE COLON - AN EXPERIMENTAL-STUDY IN THE RAT

In an experimental study, resembling a clinical trial of preoperative irradiation, 10 + 10 Gy was given to the pelvic and lower abdominal re gion of rats with a 4-day interval. The early effect on the colonic wa ll was evaluated by myeloperoxidase activity and hydroxyproline conten t of the bowel wall and correlated to histological findings. Groups of animals were followed up to eight months after irradiation for evalua tion of later effects. General effects of irradiation were seen as low WBC during the first week and delayed body weight development up to t wo months after irradiation. Local effect in the colonic wall was note d as an increase in myeloperoxidase activity (indicating a leucocyte a ccumulation) in irradiated parts of colon during the first 11 days and again significantly elevated after two months in parts of colon, irra diated as well as protected. This correlated well with histological fi ndings of inflammatory reaction, atypia and dysplasia during the first 10 days after irradiation but not at two months after irradiation. Hy droxyproline content was not affected. There were no major complicatio ns due to irradiation seen in the late course of the study period.