Changes in Growth, Morphology, and Physiology of Tetrahymena pyriformis Exposed to Continuous Cesium-137 and Cobalt-60 Gamma-Radiation.

This study investigated the effects of gamma-radiation on Tetrahymena pyriformis. The experimental approach consists of exposing T. pyriformis growing in presence of Cesium-137 (Cs) at dose rates of 1, 2, 4, and 6 cGy h and Cobalt-60 (Co) at dose rates of 8, 10, 15, and 20 cGy h. The radiation doses effects on growth, morphology, some metabolic enzymes, and reactive oxygen species (ROS) markers have been evaluated. When cells were growing in irradiating conditions at dose rates beyond 4 cGy h, a decreasing of cells and generation numbers with a prolongation of generation time and a change of morphological aspect with rounding-off of cells were observed compared to the control. The 50%-inhibitory dose (ID) for radiation was estimated at 1568.72 ± 158.45 cGy. The gamma-radiation at dose rates more than 6 cGy h, affected both glyceraldehyde 3-phosphate dehydrogenase and succinate dehydrogenase by inhibiting their activities. All of these effects were more pronounced when cells were irradiated at the dose rate of 20 cGy h using Co source. For ROS markers generated by gamma-radiation in T. pyriformis, the results showed an increase of the lipid peroxidation in cells grown in presence of gamma-radiation at dose rates more than 6 cGy h and an enhancement in catalase and superoxide dismutase activities from the dose rate of 1 cGy h. These encouraging results suggested the use of T. pyriformis as a unicellular model cell to investigate other aspects of the response to ionizing radiation.