Antioxidant status in humans after exposure to hyperbaric oxygen

Hyperbaric oxygen (HBO) treatment (i.e., exposure to 100% oxygen at a press ure of 2.5 atmosphere absolute (ATA) for a total of 3 x 20 min periods) of human subjects induced DNA damage in the alkaline comet assay with leukocyt es and protected against the DNA damaging effects of subsequent in vivo HBO exposures. Furthermore, blood taken 24 h after the first HBO was well prot ected against the in vitro induction of genotoxic effects by hydrogen perox ide. To investigate the mechanisms which led to this apparent adaptive resp onse, we determined the antioxidant status of blood from subjects before an d after HBO. We did not find differences in the plasma concentrations of th e antioxidant vitamins A, C and E after HBO treatment. HBO had also no effe ct on the 'antioxidant power' of the plasma as measured with the FRAP-assay or on the concentration of reduced glutathione determined in the plasma or in lymphocytes. Red cell concentrate activities of superoxide dismutase, c atalase, glutathione peroxidase were not influenced by HBO. In contrast, sy nthesis of the heat shock protein HSP70 which has been implicated to play a n important role in cellular protection against oxidative stress, was signi ficantly induced in lymphocytes after a single HBO treatment. To investigat e whether intake of antioxidants may protect against HBO-induced DNA damage , we supplemented subjects with vitamin E (800 mg for 7 days) or with N-ace tylcysteine (400 mg, 1 h before the HBO treatment). However, these suppleme ntations did not influence the induction of DNA damage by HBO. (C) 1999 Els evier Science B.V. All rights reserved.