Immune function in rats following repetitive exposures to 7 ATA air.
BACKGROUND
The precise action of the immunological effects associated with hyperbaric exposure is poorly understood. This study's goal was to clarify the effects and etiology of deep air dives on the immune response.


METHODS
Sprague-Dawley rats were exposed to 7-ATA air for 60 min twice daily for 3 consecutive days. Several markers of immune function, the degree of stress, and oxidative stress following or during the exposures were determined. Rats exposed to 1.47-ATA oxygen or 7-ATA nitrox (0.21-ATA oxygen + 6.79-ATA nitrogen) were taken as controls.


RESULTS
Peripheral lymphocytes and CD3+ and CD4+CD3+ subsets in peripheral blood and spleen, plasma interleukin-2 level, and the responses of splenic lymphocytes to concanavalin A all decreased, antioxidant enzyme activities and the concentration of reduced glutathione both decreased, while the level of malondialdehyde increased following hyperbaric air exposures. All changes returned to normal in 3-5 d. Similar changes were observed following exposures to 1.47-ATA oxygen, but not to normoxic nitrox. Plasma levels of adrenocorticotropic hormone and corticosterone increased after one exposure and recovered to normal levels after three exposures in rats treated with either hyperbaric or normobaric air. Pretreatment of the animals with N-acetylcysteine, a potent free radical scavenger and antioxidant attenuated the effects of hyperbaric air on immune and antioxidant systems.


CONCLUSIONS
These results are consistent with the hypothesis that repetitive exposure to 7-ATA air has a temporary immunosuppressive effect on rats, which is related to oxidative stress induced by the high partial pressure of oxygen in breathing gas.
Xu
Wei-Gang
WG
Department of Diving Medicine, Faculty of Naval Medicine, Second Military Medical University, Shanghai, China. wgxu@hotmail.com
Tao
Heng-Yi
HY
Liu
Yun
Y
Sun
Xue-Jun
XJ
Jiang
Chun-Lei
CL
D000337:Aerospace Medicine; D000818:Animals; D001274:Atmospheric Pressure; D003664:Decompression / Q000009:adverse effects*; D006931:Hyperbaric Oxygenation / Q000009:adverse effects*; D007107:Immune System; D007165:Immunosuppression Therapy; D007222:Inert Gas Narcosis / Q000209:etiology*; D008297:Male; D018384:Oxidative Stress; D051381:Rats; D017207:Rats, Sprague-Dawley; D013601:T-Lymphocytes