Investigations about the effect of radioprotective substances after irradiation of mice with fast neutrons

Several protective substances and their effects were tested within the frame of a radiobiological investigation with fast neutrons on mice. The following substances with an obviously resistance-raising effect in X-ray or γ-radiation were tested: p-aminopropionic phenon (PAPP), cystamine, 5-hydroxytryptamine (Serotomine), liposaccharide of E-coli (LPS), chlortrianisen, and 5-2/3 aminopropylaminoethylthiophosphate. The substances were all but one injected inhaperitroneally; chlortrionisen was given subcutaneously. The LDsub(50/30d) was chosen as a basis for the evaluation of the test results. The dose reduction factor (DRF) was used as quantitative measure for the protective effect of a substance. The results show that the radiation-resistance-raising effect of the substances mentioned above is clearly lower in neutron radiation of mice than in X-ray radiation. Some experiments showed no resistance-increasing effects at all. The corresponding mechanisms of the substances and their protective effect one discussed on various tissues. The results obtained might help to find substances inducing an increased radiation resistance in the future even if cells and tissues of mammals are exposed to radiation of high LET. (GSE)