Effect of sodium and acetate ions on 8-hydroxyguanine formation in irradiated aqueous solutions of DNA and 2'-deoxyguanosine 5'-monophosphate.

PURPOSE

The aim of this work was to study the combined effect of sodium and acetate ions on the radiation yield of 8-hydroxyguanine (8-OHG), one of the major DNA base lesions induced by free radicals.

MATERIALS AND METHODS

Aqueous solutions of DNA and 2'-deoxyguanosine 5'-monophosphate (dGMP) with various concentrations of sodium acetate and sodium perchlorate were γ-irradiated, enzymatically digested and analyzed by high-performance liquid chromatography (HPLC) methods.

RESULTS

It was found that both salts decrease the 8-OHG radiation yield in the concentration range studied for both DNA and dGMP, except in the case of dGMP wherein an increase in yield occurs in the concentration range from 0.1-1 mM. The dependence of the 8-hydroxy-2'-deoxyguanosine radiation yield on the concentration of both sodium acetate and sodium perchlorate have different shapes and have steeper slopes for the DNA compared with the dGMP solutions.

CONCLUSIONS

The observed decrease in the radiation yield of 8-OHG with increasing concentrations of sodium acetate is consistent with the hypothesis that sodium acetate produces two concentration-dependent effects in the DNA solutions: (1) A conformational change in the DNA caused by Na(+) counterions; and (2) free radical reactions related to the radiolysis of acetate ion.