[Formation of 8-hydroxyguanine upon damage of guanine nucleotides by gamma radiation].

Formation of 8-hydroxyguanine derivatives caused by the exposure of aqueous solutions of guanine nucleosides and nucleotides (Guo, dGuo, GMP, dGMP, GDP, and GTP) to gamma-radiation was studied by differential UV-spectroscopy. 8-hydroxyguanine had linear dose-yield relationship with G-value (radiation-chemical yield) of 0.2-0.4 molecules per 100 eV. Data on irradiation of D2O solutions of nucleotides show that the mechanism of gamma-radiation-induced formation of 8-hydroxyguanine is probably different from that of heat-induced one. Levels of intracellular guanine nucleotide pool damage caused by natural background radiation and induced by heat were compared for different temperatures. Level of DNA precursor pool damage by natural background radiation at 37 degrees C is insignificant and comprises approximately 0.2% of the heat-induced damage but rises sharply as the temperature decreases. The possible biological consequences of gamma-radiation-induced damage of guanine and deoxyguanine nucleotide cell pools are discussed.