[The radiosensitivity change of human blood lymphocytes in different mitotic cycles after a low dose irradiation]

The adaptive response (AR) in stimulated blood lymphocytes (8 donors) have been studied by two methods: analyses of unstable chromosome aberrations in metaphases and micronuclei assay (MN) with cytochalasine cytokinetic block. The adaptive irradiation in the dose of 5 cGy have been conducted 24 h and challenge irradiation after 48 h after stimulation. For the metaphase analysis of the first and subsequent mitosis cells were incubated with BrdU and were fixed 50, 72 and 96 h after the stimulation. In the MN test cells were fixed 72 or 96 h after the stimulation and cytochalasin B was added in the cell culture 24 h before fixation. Was shown that in the cells of first mitoses fixed at 50 h after stimulation only chromatid aberrations are presented in the lymphocytes of all donors and AR in all donors was noticed; but when fixation was conducted 72 h after stimulation the chromosome type aberrations are prevailing and AR is absent, 96 h after--one donor has AR. Was discovered that in the cells of the second mitosis fixed at 72 h after stimulation the only chromosome type aberrations observed, their frequency is higher that in the lymphocytes of 1 and 3 mitosis in the same fixation time, in 7 of 8 donors there is AR registered. In the cells of 3th mitosis 72 h fixation time only 1 donor has AR, in cells of the 4th mitosis nobody have AR. By the MN assay AR in two donors is observed, in the first--the increase in radiosensitivity after adapting irradiation is noticed in the rest of the radiosensitivity is not changed. 78 percent of results coincidence by MN assay with time fixation 72 and 96 h with the results of metaphase analysis in the cells of first mitosis in the same time fixation was observed. The proposition of these data explanation is that the decrease of chromatid and chromosome aberration frequency is the one is result of different enzyme systems function and the ability to the these system induction in different cells is different. If the one is decreasing the chromatid aberrations frequency is induced in lymphocytes of most donors, the second is induced rarely only in the part of cells.