CHANGES IN THE SENSITIVITY OF X-IRRADIATED MICE TO BACTERIAL ENDOTOXIN

When endotoxin was injected into mice 4 to 24 hours after X-irradiation the LD50/3 was increased from 500 μg (non-irradiated control) to 715 μg and 825 μg respectively. Administration of different doses of X-irradiation showed that increasing the dose from 200 to 600 R caused a linear increase in the endotoxin LD50 of mice and it was in the order of 100 μg per 200 R. From 800 R to 1400 R there was a decrease in the endotoxin LD50 of mice, but only the 1400-R dose produced a lower LD50 than that in the non-irradiated control. Since whole-body counter studies with 51Cr-labelled endotoxin showed that X-irradiation did not change endotoxin excretion, increased endotoxin LD50 values 4 and 24 hours after X-irradiation were not due to increased rates of endotoxin excretion.