We previously found that low-dose X-ray irradiation or radon (weak α-ray) inhalation increases SOD activities and reduces lipid peroxide levels in various organs of 7-week-old rats or rabbit. In this study, we examined how the changes of SOD activity, lipid peroxide level, and membrane fluidity of the cerebral cortex in aged male Wistar rats (65 and 91 weeks old) were affected by low-dose X-ray irradiation (100 cGy or under) compared with those in 7-week-old rats, to elucidate the mechanism of aging inhibition. The following results were obtained: Although radiation sensitivity was observed to decreases with age, low-dose irradiation changed the Mn-SOD activity, lipid peroxide level, and membrane protein fluidity parameter of the cerebral cortex in the aged rats to be closer to those in the youth. These finding suggest that the increased SOD activity induced by low-dose irradiation enhances biomembrane functions, and that the decrease of lipid peroxide level enhances the membrane protein fluidity.
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