Lipid peroxidation, DNA damage, and cellular morphology of R1 Rhabdomyosarcoma cell line irradiated in vitro by gamma-rays with different dose rates

The study examines the relationship between lipid peroxidation, DNA damage, and cell morphology after the exposure of R1 Rhabdomyosarcoma cells to two different dose-rates of gamma rays. Exponential cultures of R1 cells were irradiated with single dose of 5 Gy at high dose rate (0.833 Gy/min) and low dose rate (0.0707 Gy/min). The concentration of two aldehydes, malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE), were determined. DNA damage induction and repair were measured by using the alkaline version of the comet assay. Cellular alteration was also estimated microscopically as was the frequency of cells with micronuclei and proportion of apoptosis and necrosis. These parameters were evaluated immediately (time 0) and after different times up to 48 h of incubation in 37 degrees C, after irradiation. Results indicate that a low dose rate in comparison to high dose rate caused a significantly higher increase of aldehydes concentration observed at 12 h, followed by obviously higher DNA damage at 48 h and altered cellular morphology. The inverse dose-rate effect estimated for the gamma rays Co-60 source was found to be related to the measured biochemical and morphological parameters.