Hormesis Of Low Dose Radiation And Its Mechanism Of Signal Transduction

Objective: Study whether the supernatant ("the plasma after low dose radiation"or "the stimulating fluid") extracted through centrifugalization from blood or myeloid cells suspension after low dose radiation in vitro can produce hormesis on the cells after radiation damage or normal cells. Observe the changes of O₂^ˉ, the second messenger and c-fos, the third messenger. Probe the mechanism of signal transduction. Methods: Firstly, one healthy adult's blood was irradiated by 10cGy and 10Gy. In 1640 culture fluid containing PHA, the two specimens and the identical adult's peripheral blood were cultured in vitro respectively. The method of 3H-TdR incorporation was adopted to measure the reproductive activity of blood cells. Following these methods, co-culture in various ways of combination the normal plasma and "the plasma after low dose radiation"(the plasma extracted through centrifugalization from the blood after 10cGy radiation) with the blood cells irradiated by 10Gy and the normal blood cells, and then detect the reproductive activity of the respective group of cells. Secondly, the mouse myeloid cell suspension was irradiated respectively by 0Gy, 2Gy and 5Gy, and cultured in vitro. Measure the reproductive activity of cells by means of MTT chromatometry. Co-culture "the stimulating fluid"(the supernatant extracted through centrifugalization from the mouse myeloid cell suspension after low dose radiation of 6cGy) with the myeloid cell suspension irradiated by 0Gy, 2Gy or 5Gy, and study the reproductive activity of the respective group of cells. Meanwhile, Cytochrome C reduction method was used to determine the concentration of O₂^ˉ, the second messenger; the immunohistochemical method to test the proteinum expression of c-fos, the third messenger. Lastly, decrease or increase the concentration of O₂^-by adding DPI or PMA, and try to find out the effect of such changes on "the stimulating fluid". Results: Low dose radiation promotes the proliferation of cells, while large dose radiation lowers the reproductive activity. "The plasma after low dose radiation"can create the stimulating effect that is very evident on human blood cells after large dose radiation,enhance the reparation of cells after radiation damage and promote the proliferation of normal blood cells. Co-cultured with "the stimulating fluid", the myeloid cells after large dose radiation or the normal myeloid cells rank above the control group in the reproductive activity, which is in direct proportion to both the concentration of O2ˉand the proteinum expression of c-fos. Decreasing the concentration of O2ˉmay degrade the proliferation of the cells after radiation damage; while increasing it may lead to the opposite result. "The stimulating fluid"can withstand the adverse effect caused by DPI. Conclusion: Low dose radiation enables the cells irradiated to produce hormesis which may promote their own proliferation, and release certain excitor substance which may promote the proliferation of the cells after radiation damage and the normal ones. That is to say, "the plasma after low dose radiation"facilitates the proliferation of the blood cells after radiation damage and the normal ones as well. Besides, "the stimulating fluid"can enhance the proliferation of the myeloid cells after radiation damage and also the normal ones. The mechanism of above-mentioned phenomena is very likely to be concerned with the increase of both the concentration of O2ˉand the expression of c-fos. Therefore, one of the mechanisms of hormesis of low dose radiation is related to the fact that low dose radiation indirectly regulates O2ˉ, the second messenger and c-fos, the third messenger.