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 tumor-bearing mice. Swiss albino male mice (7-8 weeks old) with Ehrlich solid tumor in the thigh pad were irradiated with different doses of gamma-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 tumor-bearing mice compared to the non-tumor 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 tumor-burdened 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 tumor-bearing mice probably suggest this possibility. These findings of the present work might have some serious implications as the increased radiation-damage of the distant normal organs (due to tumor burden) is likely to adversely affect the therapeutic gain.