Accurate Measurement of 8-OH-dG and 8-OH-Gua in Mouse DNA, Urine and Serum: Effects of X-ray Irradiation

Oxidative stress is believed to increase the risk of lifestyle-related diseases, such as cancer and heart disease. For the measurement of oxidative stress in vivo, 8-hydroxydeoxyguanosine (8-OH-dG) in DNA or urine is the most popular biomarker. However, there are some difficulties in the reproducible and accurate analysis of 8-OH-dG in DNA. In this study, we found that artifactual 8-OH-dG was elevated significantly with time in an analytical sample kept at 10°C, but not for one kept at -80°C. Furthermore, we developed a method for urinary 8-OH-dG analysis with high accuracy by an HPLC-ECD system, using anion-exchange- and reverse-phase-columns. This method can also be used for urinary and serum 8-hydroxyguanine (8-OH-Gua, free base) analyses, with a slight modification. By applying these improved methods, we confirmed the induction of oxidative stress with low dose (2 Gy) whole body X-ray irradiation of mice. The 8-OH-dG levels in the mouse urine were increased about 4.2-fold by 2 Gy irradiation, in a dose-dependent manner. The 8-OH-Gua levels in the serum were also increased with 2 Gy of irradiation. These results suggest that our improved 8-OH-dG and 8-OH-Gua analysis methods are useful for measurements of oxidative stress in vivo.