The Use of EPR Spectroscopy at System Analysis of Organism Radiosensitivity/Radioresistance. Experience and Tendencies
The responses of deoxyribonucleotide (dNTP), DNA and protein synthesis systems in blood-forming organs of animals (dogs, mice), as well as the changes in Fe<sup>3+</sup>-transferrin (Fe<sup>3+</sup>-TF) and Cu<sup>2+</sup>-ceruloplasmin (Cu<sup>2+</sup>-CP) pools in blood due to γ- irradiation and administration of radioprotectors have been studied. It has been shown that changes in Fe<sup>3+</sup>-TF and Cu<sup>2+</sup>-CP pools in blood serve the indices of the changes of body radioresistance and are reliably controlled by the EPR technique. An increase in the Fe<sup>3+</sup>-TF pool promotes activation of the synthesis of dNTP, DNA and Fe<sup>3+</sup>-containing proteins, which is essential for the repair efficiency during early post-irradiation time, as well as for the development of compensatory and restorative reactions of cellular systems; i.e., they are responsible for the body resistance to DNA-damaging factors. It is important that the intensity of responses depends on the initial state of the organism. It has been shown that the changes in Fe<sup>3+</sup>-transferrin and Cu<sup>2+</sup>-ceruloplasmin pools, which are trust-worthy controlled by the EPR technique in whole blood, blood plasma, and serum, as well as the changes in the extracellular DNA content in blood plasma, are markers of the changes in the organism radioresistance. The important role in the mechanism of the antiradiation activity of indometophene and indralin belongs to the increased ribonucleotide reductase activity and induction of the ribonucleotide synthesis, which provides effective reparation of the damage to the DNA of the cells in radiosensitive tissues and organs as a result of administration of radioprotectors at the optimal protective doses before radiation exposure. This has been proved during medical examination of the Chernobyl accident recovery children exposed to low-intensity radiation.