Radiation induced membrane oxidative damage in human cells at low and high dose-rate: production and repair.

A human promyelocitic cell line, HL60, has been used to study the production and repair of membrane oxidative damage after exposure to acute and fractionated doses of ionising radiation. The oxidative damage is detected at doses as low as 0.1 Gy . The dose response curve is not linear with the dose and most of the damage is produced at doses 10Gy. After exposure to an acute dose of 10 Gy cells were incubated in the growth conditions but evidences of repair were not obtained for incubation times up to 4 hours. Cells daily exposed to low doses, namely 0.1 Gy or 0.1 Gy followed by 10 hours incubation and then a second dose of 0.1 Gy, show an additive increase of the damage. In summary: (i) membrane oxidative damage can be observed after very low doses of ionizing radiation; (ii) the damage produced by fractionated doses is additive; (iii) oxidative damage is not repaired both after acute or fractionated exposures.