The Use of Parenteral Chemicals for Protection against Oral Radiation Death in Mice

The effect of parenteral administration of protective chemicals on mortality in oral radiation death was studied. The chemicals p-aminopropriophenone (PAPP), mercaptoethylamine (MEA), and aminoethylisothiuronium (AET) were administered intraperitoneally in C57Bl male mice at the following dosage levels: PAPP, 30 and 60 mg/kg in propylene glycol and water; MEA, 400 mg/kg aqueous; and AET, 225 mg/kg aqueous. Anesthetized mice were irradiated to the head in a manner to produce oral radiation death. Preirradiation MEA treatment produced an LD₅₀ of 2159 R as compared to irradiated control groups LD₅₀ of 1624 R, giving a DRF of 1.33. Similarly AET treatment produced an LD₅₀ of 1902 R compared to a control LD₅₀ of 1626 R, giving a DRF of 1.16. PAPP at 30 mg/kg produced an LD₅₀ value of 1880 R and at 60 mg/kg 2049 R, with controls at 1626 R, thus giving a DRF of 1.16 and 1.26, respectively. Further studies with PAPP as related to methemoglobinemia and under conditions of hyperbaric oxygen produced results which indicated that the protective mechanism of PAPP was independent of the degree of methemoglobinemia and protection was slightly enhanced under conditions of hyperbaric oxygen.