Radiation induced oxidative stress: I. Studies in Ehrlich solid tumor in mice

Understanding the response of tumors to ionizing radiation might potentiall y lead to improvement in tumor control and patient morbidity. Since the ant ioxidant status is likely to be linked to radioresponse, its modulation nee ds to be examined. Therefore, Swiss albino male mice (7-8 weeks old) with E hrlich solid tumors were irradiated with different doses of gamma rays (0-9 Gy) at a dose rate of 0.0153 Gy/s; and enzymes involved in antioxidant fun ctions were determined in the tumors. Radiation effects in terms of oxidati ve damage, LDH, nitric oxide and DNA fragmentation were also examined. In tumors, the specific activity of SOD was increased with dose but decline d 6 Gy onwards. GST, DTD and GSH showed an almost progressive increase. The se enhanced activities might have resulted from the increased protein expre ssion. This possibility was supported by the Western Blot analysis for GST protein. These changes might be closely linked to the radiation-induced oxi dative stress as reflected by the enhanced levels of peroxidative damage, D NA fragmentation, LDH activity and nitric oxide levels. These findings may have relevance to radiation therapy of cancer as the elevated antioxidant s tatus of irradiated tumors is likely to limit the effectiveness of radiatio n dose and adversely affect the therapeutic gain.