Enhancement of bio-functions by low-dose irradiation

The hypothesis of radiation hormesis has been proposed, and some phenomena of hormetic effect on in vivo and in vitro were observed. However, the mechanism of radiation hormesis is uncertainty even now. Therefore, to elucidate the mechanism of radiation hormesis, we investigated the literature survey and we examined changes in activities of inflamatory mediators and cytokines by low-dose whole-body X-irradiation. The results obtained were as follows; (1) Our working hypothesis for the mechanism of radiation hormesis is that mild inflammation induced by a small amount of oxygen radicals produced by low-dose irradiation stimulates immunocompetent cells and their functions. (2) Concentration of LTB4 and PGE2 being inflammatory mediators in the supernatant of mouse splenocytes suspension were increased by low-dose X-irradiation. It suggests mild inflammation was induced by low-dose irradiation. (3) Con A response of normal splenocytes were increased by cultivated in the presence of serum from low-dose irradiated mice as compared with serum from sham-irradiated mice. This phenomenon suggests that bio-activity of cytokines in serum were stimulated by low-dose irradiation. (author)