The radiosensitizing activity of dichloromethane extract of guduchi [Tinospora cordifolia (WILLD.) MIERS ex HOOK. F. & THOMS. Family: Menispermaceae (TCE)] in the mice transplanted with Ehrlich ascites carcinoma (EAC) was investigated. The EAC mice received 0, 25, 30, 40, 50 or 100 mg/kg b.wt. TCE 1 h before exposure to 6 Gy hemi-body γ-radiation and then once daily for another eight consecutive days after irradiation. The EAC mice receiving TCE for the above regimen showed a dose-dependent elevation in tumor-free survival; the highest radiosensitizing activity was observed at 30 mg/kg b. wt. TCE. Treatment of animals with 30 mg/kg b. wt. TCE, 1 h before exposure to 6 Gy of hemi-body gamma irradiation and subsequently once daily for another six consecutive days post-irradiation increased the life span of EAC mice. This is evident by more number of long-term survivors (LTS) as well as survivors beyond 120 days when compared to the group of animals that received TCE after irradiation for six consecutive days. Treatment modality was also altered to assess the radiosensitizing effect of TCE before and after irradiation. Evaluation of glutathione (GSH), glutathione S-transferase (GST) and lipid peroxidation (LPx) in mice treated with TCE 1 h before irradiation and subsequently once daily for another six days showed a significant decline in GSH up to 14 h and GST up to 24 h accompanied by a significant elevation in LPx at 12 h post-irradiation. The radiosensitization of TCE may be due to depletion of glutathione and glutathione-S-transferase, accompanied by elevated levels of lipid peroxidation and DNA damage of tumor cells. Since Tinospora cordifolia is being used in India for treatment of various ailments, it may offer an alternative treatment strategy for cancer in combination with gamma radiation.
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