DNA-damage detection in man after radiation exposure--the comet assay--its possible application for human biomonitoring.

The exposure of human beings to ionizing radiation is still of great concern to occupational and environmental medicine. The goal of this workshop is to identify a panel of biological markers that could be used in humans after exposure to ionizing radiation. The comet assay or single cell gel (SCG) assay is a new method that allows efficient determination of single-strand breaks (SSB) and double-strand breaks (DSB), as well as alkali-labile sites in the DNA of single cells. In order to demonstrate the practicability of the comet assay for the detection of DNA damage caused by low doses of ionizing radiation, we exposed human peripheral blood cells to radiation in vitro. The extent of DNA damage in blood cells irradiated with x-rays (0.05-1 Gy) was significantly increased above the control values even at 0.05 Gy and shows a clear dose-relationship. To investigate the repair kinetics for x-ray-induced DNA damage following acute and chronic (fractionated) irradiation, we exposed peripheral blood to 1 Gy and examined the tail moment at different time intervals. The effect of one acute dose is repaired within two h, whereas the effect of fractionated irradiation gives a totally different result. The tail moment of the initial damage increased indicating an accumulation of the damage, and the repair activity clearly decreased. Until now, there was no data available concerning DNA damage in vivo. For this reason, we explored patients subjected to radioiodine therapy as well as a Chernobyl liquidator.(ABSTRACT TRUNCATED AT 250 WORDS)