The intestinal radiation syndrome: sepsis and endotoxin.

Rats were whole-body irradiated with 8-MeV cyclotron-produced neutrons and 137Cs gamma rays to study the role of enteric bacteria and endotoxin in the intestinal radiation syndrome. Decrease in intestinal weight was used as an index of radiation-induced breakdown of the mucosa. Neutron and gamma-ray doses that were sublethal for intestinal death resulted in a dose-dependent decrease in intestinal weight, reaching minimal values 2 to 3 days after exposure, followed by recovery within 5 days after irradiation. Neutron and photon doses that caused intestinal death resulted in greater mucosal breakdown with little or no evidence of mucosal recovery. The presence of fluid in the intestine and diarrhea, but not bacteremia or endotoxemia, were related to mucosal breakdown and recovery. Neither sepsis nor endotoxin could be detected in liver samples taken at autopsy from animals which died a short time earlier from intestinal injury. These results suggest that overt sepsis and endotoxemia do not play a significant role in the intestinal radiation syndrome.