Endotoxin Treatment and X Irradiation in Mice Bearing Transplanted Tumors

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Abstract
Salmonella typhosa endotoxin had a small inhibitory effect on the local growth of a lymphosarcoma. X irradiation with 475 r whole-body or 1000 r (200 kv.) to the tumor alone produced the same degree of regression and, in both cases, when endotoxin was given 24 hours before irradiation an additive effect on tumor regression was seen. Whole-body irradiation of mice bearing a disseminated reticulum-cell sarcoma increased their survival time, but increasing the dose from 600 r to 1500 r (2.5 Mev) did not yield a steadily increasing survival time. Irradiation repeated at intervals of 2 weeks or more was more effective than single exposures. Endotoxin given 24 hours before irradiation increased tolerance to radiation. Endotoxin also produced an increase in survival time of the irradiated tumor-bearing mice which was greater than the sum of the increase attributable to endotoxin or radiation alone.