BIOLOGICAL SIGNIFICANCE OF DNA-DAMAGE INDUCED BY HYPERBARIC-OXYGEN

Hyperbaric oxygen (HBO) treatment as used therapeutically has been sho wn to induce DNA damage in the alkaline comet assay with leukocytes fr om test subjects, Using formamidopyrimidine-DNA glycosylase, a DNA rep air enzyme which specifically nicks DNA at sites of 8-oxoguanines and formamidopyrimidines, we have detected enhanced DNA migration, indicat ing significant oxidative base damage, after HBO treatment. Increased DNA damage was seen immediately at the end of treatment, while 24 h la ter no effect was found, We now show that HBO-induced DNA strand break s and oxidative base modifications are rapidly repaired, leading to a reduction in induced DNA effects of > 50% during the first hour. A sim ilar decrease was found in blood taken immediately after exposure and post-incubated for 2 h at 37 degrees C in vitro and in blood taken and analysed 2 h after exposure, suggesting similar repair activities in vitro and in vivo, When the same blood samples showing increased DNA d amage after HBO in the comet assay were analysed in the micronucleus t est, no indications of induced chromosomal breakage in cultivated leuk ocytes could be obtained. The results suggest that the HBO-induced DNA effects observed with the comet assay are efficiently repaired and ar e not manifested as detectable chromosome damage.