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.