Inferences from the collaboration in the field of pharmaco-chemical protection and treatment of radiation injury according to the 'intercosmos' program

A review is presented of available information on repair processes following induction by radiation of macromolecule primary structure lesions, such as formation of pyrimidine dimers in DNA. Such changes may be repaired by cellular enzymatic systems in a few hours or days. To favor these processes, use can be made of compounds, the action of which involves 'biochemical mechanisms', such as nucleotides, nucleosides, and DNA, as well as ATP, ADP, thiamin pyrophosphate, and some bacterial, yeast, and plant polysaccharides (progiygnosan, zymosan, carrageenan, etc.). Under protracted irradiation conditions, however, there may occur little, if any, repair or macromolecule primary structure lesions, such as damage to DNA bases resulting in triplet miscoding, DNA strand breaks that do not respond to intracellular enzymatic systems, or accumulation of such lesions in organs or tissues with slow renewal rates. In the case of protracted exposure, it is also essential to raise the radioresistance of the organism by stimulating repair systems in susceptible cells. Protracted radiation experiments have shown ATP to slow down the process of activation of acid DNA-ase, and this favorable ATP effect to be correlated with the extent of DNA structural anomalies induced in irradiated animals. When ATP was administered both prior to and following radiation exposure, a significant reduction in DNA single- and double-strand breaks was observed. It has also been demonstrated that ATP inhibits protein synthesis in isolated spleen nuclei by suppressing, similarly to aminothiols, particular steps in cell metabolism. Cytogenetic studies have given evidence for the ability of ATP and ADP to reduce chromosome aberration yields; and polarographic studies, that ATP added to the culture medium increases respiratory rate and enhances oxidative phosphorilation processes in liver mitochondria from irradiated animals. (A.B.)