Abstract
1. Radiotherapy has attracted increasing interest in recent years. It is known that ionizing radiation induces oxygen radical injury, whereas oxidative stress by the radiation can cause cellular responses to defense cellular injury. In this study, the metabolism of antioxidants in response to ionizing radiation to the brain was studied in the brain using experimental rabbits. 2. Ionizing radiation to the hemicerebrum caused an increase in the levels of glutathione (GSH) and the activity of a GSH synthesizing enzyme, gamma-glutamylcysteine synthetase (gamma-GCS), and Cu,Zn-superoxide dismutase (Cu,Zn-SOD). Ionizing radiation also induced DNA-damage estimated by the formation of 8-hydroxydeoxyguanosine. These changes were dependent on the radiation dose. 3. Previous intrathecal-administration of buthionine sulfoximine (100 microM), a specific inhibitor of gamma-GCS, increased DNA damage by radiation in the radiated hemicerebrum. That of S-methyl GSH, on the other hand, resulted in a significant reduction of DNA damage by radiation. 4. These results suggest that synthesis of GSH and Cu,Zn-SOD is responsive to ionizing radiation and this induction of antioxidants may play a role in reducing tissue damage in radiotherapy.