Comparative Protection by a Combination Treatment in Mice Irradiated with Fission Neutrons or X-Rays

Abstract

A triple treatment, including (1) preirradiation protection by a chemical mixture (7 μmoles of AET, 25 μmoles of MEA, and 2 μmoles of serotonin, injected intraperitoneally, 0.4 ml/mouse), (2) postirradiation administration of 5× 105 nucleated homologous bone marrow cells intravenously, and (3) daily subcutaneous injections of the antibiotic streptomycin (5 mg in 0.5 ml of saline), for 10 days after irradiation, was used in CF No. 1/ANL mice exposed to single supralethal whole-body doses (400 to 600 rad) of either fission neutrons (CP-5 Reactor) or 900 to 1700-R doses of 250-kVp x-rays. Irradiations of each group of mice were completed in less than an hour. In the x-irradiated mice this multiple treatment elevated the ${\rm LD}_{50(30)}$ from approximately 675 R to more than 1700 R, a dose-reduction factor (DRF) in excess of 2.5. In comparison, the ${\rm LD}_{50(30)}$ for neutron-exposed animals was increased by a factor of less than 1.3. When the pre-x-irradiation treatment with the chemical mixture was u...