[Protective action of radioprotectors and shielding against high-energy protons in experiments with rats].

Experiments with male rats were staged to study effectiveness of radioprotectors of two classes of chemical compounds (aminothiols--cystamine and indolyl alkylamines--mexamine and indralin) against high-energy protons (120 MeV) at a minimal absolutely lethal dose (10 Gy) and more than lethal doses (11.0-14.0 Gy). The best protective effect was provided by intraabdominal indralin at a dose of 75 mg/kg. However, this protective effect of indralin weakens with a dose rise and fades away with the dose rising to the absolutely lethal or more than lethal level (14.0 Gy). Investigations of the effectiveness of shielding different segments of the rat's body from high-energy protons (120 MeV) at more than lethal doses showed a substantial reduction and then full loss of the shielding protective action. Evaluation of the effectiveness of combined protection (radioprotectors plus shielding) against high-energy protons at more than lethal doses led to the conclusion about an additive (at 1.0-13.0 Gy) or potentiative (at 14.0 Gy) effect. For instance, indralin (75 mg/kg) and shielding of the abdomen increased rat's survivability to 89.7% after exposure at 11.0-13.0 Gy and to 87.5% after exposure at 14.0 Gy. It should be kept in mind that the radioprotective action of this combination was also observed during exposure to more than lethal doses when the protective effect of shielding and chemical compounds is minimal or lost altogether.