Investigation of the effects of ionizing radiation on radiation-induced bystander changes in the cells of the blood system of mice at the inter-organism level

The study was aimed at the task to determine the radiation-induced “bystander effects” at the inter-organism level. In the experiment, irradiated and non-irradiated mice kept together were used. The mice were irradiated at a dose of 3 Gy at a research radiobiological gamma-ray facility with sources of Cs-137. The number of leukocytes and the relative number of lymphocytes in peripheral blood of mice were evaluated at 3, 7, 14, 30, 60 and 90 days after the irradiation. In unirradiated “bystander” mice kept with irradiated animals, both in cages without a septum and with a septum, a possible tendency to decrease the number of leukocytes compared to the same indicators in biological control was found. When analyzing the relative number of lymphocytes, a tendency to decrease in this indicator in “bystander” mice both when kept without a partition and with a partition was shown. In unirradiated bystander animals when kept with irradiated animals in a cage with a partition, a statistically significant decrease in the relative number of lymphocytes in peripheral blood was recorded: at the 3-rd day (t=2.13; p=0.047), at the 30-th day (t=2.94; p=0.01) and at the 90-th day (t=3.07; p=0.01) after irradiation, as well as when kept in the same cage with irradiated mice without a partition at the 60-th day (t=2.24; p=0.038) after the start of the experiment. This result can be considered as a radiation-induced “bystander effect” in unirradiated animals. In irradiated animals, which were kept together with unirradiated animals in the cage with a partition, a statistically significant increase in the relative number of lymphocytes was recorded at the 3-rd day (t=2.6; p=0.02), 14-th day (t=2.61; p=0.018) and at the 60-th day (t=2.38; p=0.03) after irradiation, so the radiation-induced “rescue effect” was obtained. Based on the data obtained in this experiment, it is assumed that the radiation-induced “bystander effect” may be reversed, that is, unirradiated organisms are able to reduce radiation-induced effects in irradiated individuals ‒ the “rescue effect”.