Abstract
Lymphocytes isolated from bovine blood were irradiated at doses of 0.5, 1.0 and 1.5 Gy with dose-rates of 0.361 0.150, 0.062, and 0.006 Gy per min. The amount of trypan blue negative cells were counted directly after radiation and eight hours after the onset of the radiation, and compared with control cells. A considerable decrease of cells was found especially at the lowest dose-rate. At this low dose-rate, radiation induced cell loss already occurred during the irradiation period. These experiments suggest that the observed inverse dose-rate effects on lympocyte survival are caused by radiation induced damage to the plasma membrane of the cell. This phenomenon is especially pronounced at the lower range of dose-rates and is interpreted as a result of slowly progressing chain reactions occurring in the membranes, initiated by ionizing radiation.
