Effect of age on the induction of 8-oxo-2′-deoxyguanosine-releasing enzyme in rat liver by γ-ray irradiation

Changes in the 8-oxodG content of nuclear DNA in Fischer 344/DuCrj rat liver after γ-ray irradiation. DNA was extracted from the livers of rats 6 months (●) and 27 months (▴) of age exposed to 5 Gy of γ-rays. Each value represents the mean±SD (n=5). The contents of 8-oxodG in the livers of young and aged rats without γ-irradiation are shown by the dotted line (⋯) and the broken line (- - -), respectively. *Significantly different from the 8-oxodG level in control rats at P<0.001. **Significantly different from the 8-oxodG level in control rats at P<0.01. ***Significantly different from the 8-oxodG level in control rats at P<0.05.

Elution profiles of 8-oxodG-releasing enzymes in the fractions eluted from phosphocellulose column chromatography of homogenates of livers from rats 6 months of age 2 h after γ-ray irradiation. Chromatography was carried out as described in Section 2. Fractions were treated with substrate (γ-ray-irradiated calf thymus) DNA, and enzyme activities were estimated from the amount of free 8-oxodG detected by the HPLC/ECD system. The concentration of KCl in the elution buffer is shown by the broken line.

Elution profiles of enzymes that release 8-oxodG mono- and/or di-phosphate in fractions of γ-ray-irradiated rat liver eluted from phosphocellulose column chromatography of homogenates of livers from rats 6 months of age 2 h after γ-ray irradiation. Chromatography was carried out as described in Section 2. Fractions of rat liver homogenates were treated with substrate DNA and then with alkaline phosphatase. Enzyme activities were estimated from the amount of free 8-oxodG detected by the HPLC/ECD system. The concentration of KCl in the elution buffer is shown by the broken line.

Elution profiles of enzymes that cleave on the 3′-side of 8-oxodG residues in the fractions eluted from phosphocellulose column chromatography of liver homogenates from rats 6 months of age 2 h after γ-ray irradiation. Chromatography was carried out as described in Section 2. Fractions of rat liver homogenates were treated with the substrate DNA and then with exonuclease III and alkaline phosphatase. Enzyme activities were estimated from the amount of free 8-oxodG detected by the HPLC/ECD system. The concentration of KCl in the elution buffer is shown by the broken line.

Elution profiles of enzymes that cleave on the 5′-side of 8-oxodG residues in the fractions eluted from phosphocellulose column chromatography of liver homogenates from rats 6 months of age 2 h after γ-ray irradiation. Chromatography was carried out as described in Section 2. Fractions of rat liver homogenates eluted from the chromatography of liver homogenates of rats were treated with the substrate DNA and then with phosphodiesterase II and alkaline phosphatase. Enzyme activities were estimated from the amount of free 8-oxodG detected by the HPLC/ECD system. The concentration of KCl in the elution buffer is shown by the broken line.

Changes in the 8-oxodG-releasing enzyme activities in the livers of rats 6 months (●) and 27 months (▴) of age exposed to γ-ray irradiation. The 8-oxodG-releasing activity was estimated from the amounts of free 8-oxodG in Peak 2 using Method 2. Each value represents the average of two separate experiments.