LAUSR

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 ( 137 Cs) at dose rates of 1, 2, 4, and 6 cGy h −1 and Cobalt-60 ( 60 Co) at dose rates of 8, 10, 15, and 20 cGy h −1 . 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 −1 , 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 50 ) for radiation was estimated at 1568.72 ± 158.45 cGy. The gamma-radiation at dose rates more than 6 cGy h −1 , 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 −1 using 60 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 −1 and an enhancement in catalase and superoxide dismutase activities from the dose rate of 1 cGy h −1 . These encouraging results suggested the use of T. pyriformis as a unicellular model cell to investigate other aspects of the response to ionizing radiation.