Hemoglobin mass and intravascular volume kinetics during and after exposure to 3,454-m altitude.
High altitude (HA) exposure facilitates a rapid contraction of plasma volume (PV) and a slower occurring expansion of hemoglobin mass (Hbmass). The kinetics of the Hbmass expansion has never been examined by multiple repeated measurements, and this was our primary study aim. The second aim was to investigate the mechanisms mediating the PV contraction. Nine healthy, normally trained sea-level (SL) residents (8 males, 1 female) sojourned for 28 days at 3,454 m. Hbmass was measured and PV was estimated by carbon monoxide rebreathing at SL, on every 4th day at HA, and 1 and 2 wk upon return to SL. Four weeks at HA increased Hbmass by 5.26% (range 2.5-11.1%; P < 0.001). The individual Hbmass increases commenced with up to 12 days of delay and reached a maximal rate of 4.04 ± 1.02 g/day after 14.9 ± 5.2 days. The probability for Hbmass to plateau increased steeply after 20-24 days. Upon return to SL Hbmass decayed by -2.46 ± 2.3 g/day, reaching values similar to baseline after 2 wk. PV, aldosterone concentration, and renin activity were reduced at HA (P < 0.001) while the total circulating protein mass remained unaffected. In summary, the Hbmass response to HA exposure followed a sigmoidal pattern with a delayed onset and a plateau after ∼3 wk. The decay rate of Hbmass upon descent to SL did not indicate major changes in the rate of erythrolysis. Moreover, our data support that PV contraction at HA is regulated by the renin-angiotensin-aldosterone axis and not by changes in oncotic pressure.
Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland; Department of Environmental Physiology, School of Technology and Health, Royal Institute of Technology, Solna, Sweden; chrsie@kth.se.
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Siebenmann
Institute of Human Movement Sciences and Sport, ETH Zürich, Zürich, Switzerland;
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Cathomen
Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland;
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M
Hug
Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland;
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Keiser
Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland;
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AK
Lundby
Intensive Care Unit, University Hospital of Zürich, Zürich, Switzerland;
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http://orcid.org/0000-0002-2765-881X
MP
Hilty
Department of Clinical Biochemistry, Copenhagen, and Aarhus University, Aarhus, Denmark;
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JP
Goetze
H. Lundbeck, Valby, Denmark; and.
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Rasmussen
Center for Integrative Human Physiology, Institute of Physiology, University of Zürich, Zürich, Switzerland; Food and Nutrition and Sport Science, Gothenburg University, Gothenburg, Sweden.
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Lundby
D000222:Adaptation, Physiological / Q000502:physiology*; D000328:Adult; D000531:Altitude; D001810:Blood Volume / Q000502:physiology*; D004909:Erythrocyte Indices / Q000502:physiology*; D005260:Female; D006454:Hemoglobins / Q000502:physiology; D006801:Humans; D007700:Kinetics; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D055815:Young Adult
D006454:Hemoglobins
blood; erythropoietin; hypoxia; oxygen; plasma volume