Radiation induced oxidative stress: II Studies in liver as a distant organ of tumor bearing mice

Since the radiation dose tolerance of normal tissues/organs away from the site of tumor influences the success of radiation therapy of cancer, and antioxidant status is likely to be one of the factors to determine the tolerance; the radioresponse of antioxidant enzymes has been examined in the liver as a representative distant organ in the tumorbearing mice.Swiss albino male mice (7–8 weeks old) with Ehrlich solid tumor in the thigh pad were irradiated with different doses of radiation (0–9 Gy) at a dose rate of 0.0153 Gy/s and the specific activities of enzymes involved in the free radical metabolism were determined in the liver. Except GST, the activities of SOD, DTD and Gly I as well as the GSH content were found to be higher in the liver of tumorbearing mice compared to the nontumor bearing mice. The catalase activity progressively decreased with dose in both the groups of mice. However, the activity was relatively higher in the liver of tumor bearing mice than the control. Thus, the radioresponse of antioxidant enzymes seemed to be significantly different in the liver of tumorburdened mice compared to controls. The enhanced activities might be due to relatively more damage caused by radiation. The higher levels of NO· and peroxidative damage in the liver of tumorbearing mice probably suggest this possibility. These findings of the present work might have some serious implications as the increased radiationdamage of the distant normal organs (due to tumor burden) is likely to adversely affect the therapeutic gain.