Acute short-term hyperoxia followed by mild hypoxia does not increase EPO production: resolving the "normobaric oxygen paradox" |
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Authors: | Debevec Tadej Keramidas Michail E Norman Barbara Gustafsson Thomas Eiken Ola Mekjavic Igor B |
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Institution: | (1) Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia;(2) Jozef Stefan International Postgraduate School, Ljubljana, Slovenia;(3) Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institute, Stockholm, Sweden;(4) Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden |
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Abstract: | Recent findings suggest that besides renal tissue hypoxia, relative decrements in tissue oxygenation, using a transition of
the breathing mixture from hyperoxic to normoxic, can also stimulate erythropoietin (EPO) production. To further clarify the
importance of the relative change in tissue oxygenation on plasma EPO concentration EPO], we investigated the effect of a
consecutive hyperoxic and hypoxic breathing intervention. Eighteen healthy male subjects were assigned to either IHH (N = 10) or CON (N = 8) group. The IHH group breathed pure oxygen (FiO2 ~ 1.0) for 1 h, followed by a 1-h period of breathing a hypoxic gas mixture (FiO2 ~ 0.15). The CON group breathed a normoxic gas mixture (FiO2 ~ 0.21) for the same duration (2 h). Blood samples were taken just before, after 60 min, and immediately after the 2-h exposure
period. Thereafter, samples were taken at 3, 5, 8, 24, 32, and 48 h after the exposure. During the breathing interventions,
subjects remained in supine position. There were significant increases in absolute EPO] within groups at 8 and 32 h in the
CON and at 32 h only in the IHH group. No significant differences in absolute EPO] were observed between groups following
the intervention. Relative (∆EPO]) levels were significantly lower in the IHH than in the CON group, 5 and 8 h following
exposure. The tested protocol of consecutive hyperoxic-hypoxic gas mixture breathing did not induce EPO] synthesis stimulation.
Moreover, the transient attenuation in ∆EPO] in the IHH group was most likely due to a hyperoxic suppression. Hence, our
findings provide further evidence against the “normobaric O2 paradox” theory. |
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