A Cytogenetic Comparison of the Responses of Mouse and Human Peripheral Blood Lymphocytes to ⁶⁰Co γ Radiation

Experiments were conducted to compare the chromosome damaging effects of ⁶⁰Co γ radiation on mouse and human peripheral blood lymphocytes (PBLs). Either whole blood or isolated and pelleted mononuclear leucocytes (MNLs) were irradiated with a ⁶⁰Co unit to yield exposures of 1, 2, 3, or 4 Gy. In addition, mice were whole-body irradiated in vivo with the same doses so that an in vitro-in vivo comparison could be made. The results indicate that mouse PBLs irradiated in whole blood, whether in vivo or in vitro, respond similarly to ⁶⁰Co γ rays as measured by dicentric chromosome formation. In addition, mouse and human PBLs showed a similar radiosensitivity, but because the mouse PBL data were best fitted to an exponential function and the human PBL data to a quadratic function, direct comparisons were difficult to make. Pelleted MNLs from mice were much less sensitive to the clastogenic effects of γ radiation than whole blood. This is believed to be due to hypoxic conditions that developed during irradiation and transport. Human PBLs did not show a marked difference whether irradiated in whole blood or as pelleted MNLs in tissue culture medium.