Abstract: Objective The radiation resistance of naked mole-rats and mice and their skin fibroblasts were investigated by gamma ray irradiation at different doses and frequencies. Methods Adult mice (8 weeks old) and adult naked mole-rats (52 weeks old) were treated with ⁶⁰Co gamma ray irradiation in low doses by multi-times or high doses one-time, respectively, to analyze their basic vital signs, changes in peripheral blood lymphocytes and pathological changes in major organs. Skin fibroblasts from naked mole-rats and mice were irradiated with different dosages to detect the damage of reactive oxygen species (ROS). Results Thirty days after one-time irradiation with 6 Gy, the survival rate of mice was 30%, and the ratio of helper T lymphocytes and killer lymphocytes (CD4+/CD8+) and dendritic cells (DC) in their peripheral blood showed no significant change. However, the survival rate of naked mole-rats on day 30 was 100%, CD4+/CD8+ in peripheral blood increased significantly on day 4 after irradiation, and DC percentage increased first and then decreased sharply. After repeated irradiation with low dosage, the bone marrow, thymus, liver and spleen and other major tissues and organs of mice all showed different degrees of lesions, while the corresponding organs of naked mole-rats showed no obvious abnormalities. There was not any significant change in ROS in skin fibroblasts of naked mole-rats and mice irradiated by 6 Gy dose. But, under radiation of 50 Gy doses, the oxygen injury of skin fibroblasts of naked mole-rats was significantly lower than that of mouse skin fibroblasts. Conclusion Naked mole rats have natural resistance to ionizing radiation. Their vital signs, morphology and functions of tissues and organs have not changed markedly due to external radiation factors, and their immune level is activated. Skin fibroblasts of naked mole-rats also exhibit anti-ionizing radiation properties.

Key words: Naked mole-rat, Radiation resistant, Immunology