title: PlanHab: Hypoxia counteracts the erythropoietin suppression, but seems to exaggerate the plasma volume reduction induced by 3 weeks of bed rest.
abstract: The study examined the distinct and synergistic effects of hypoxia and bed rest on the erythropoietin (EPO) concentration and relative changes in plasma volume (PV). Eleven healthy male lowlanders underwent three 21-day confinement periods, in a counterbalanced order: (1) normoxic bed rest (NBR; PIO2: 133.1 ± 0.3 mmHg); (2) hypoxic bed rest (HBR; PIO2: 90.0 ± 0.4 mmHg, ambient simulated altitude of ~4000 m); and (3) hypoxic ambulation (HAMB; PIO2: 90.0 ± 0.4 mmHg). Blood samples were collected before, during (days 2, 5, 14, and 21) and 2 days after each confinement to determineEPOconcentration. Qualitative differences inPVchanges were also estimated by changes in hematocrit and hemoglobin concentration along with concomitant changes in plasma renin concentration.NBRcaused an initial reduction inEPOby ~39% (P = 0.04). By contrast,HBRenhancedEPO(P = 0.001), but the increase was less than that induced byHAMB(P < 0.01). All three confinements caused a significant reduction inPV(P < 0.05), with a substantially greater drop inHBRthan in the other conditions (P < 0.001). Thus, present results suggest that hypoxia prevents theEPOsuppression, whereas it seems to exaggerate thePVreduction induced by bed rest.
authors.affiliation: Department of Environmental Physiology, Swedish Aerospace Physiology Center, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden michail.keramidas@sth.kth.se.
authors.forename: Michail E
authors.initials: ME
authors.lastname: Keramidas
authors.affiliation: Department of Automation, Biocybernetics and Robotics, Jozef Stefan Institute, Ljubljana, Slovenia.
authors.forename: Igor B
authors.initials: IB
authors.lastname: Mekjavic
authors.affiliation: Department of Environmental Physiology, Swedish Aerospace Physiology Center, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Roger
authors.initials: R
authors.lastname: Kölegård
authors.affiliation: Department of Anaesthesiology, Stress and Immunology Lab, University of Munich, Munich, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Choukèr
authors.affiliation: Department of Anaesthesiology, Stress and Immunology Lab, University of Munich, Munich, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Strewe
authors.affiliation: Department of Environmental Physiology, Swedish Aerospace Physiology Center, School of Technology and Health, Royal Institute of Technology, Stockholm, Sweden.
authors.forename: Ola
authors.initials: O
authors.lastname: Eiken
mesh_terms: D000203:Activities of Daily Living; D000328:Adult; D001510:Bed Rest / Q000009:adverse effects*; D015415:Biomarkers / Q000097:blood; D001794:Blood Pressure; D015536:Down-Regulation; D004921:Erythropoietin / Q000097:blood*; D015444:Exercise; D064368:Healthy Volunteers; D006339:Heart Rate; D006801:Humans; D020896:Hypovolemia / Q000097:blood / Q000209:etiology* / Q000503:physiopathology; D000860:Hypoxia / Q000097:blood / Q000150:complications* / Q000503:physiopathology; D008297:Male; D009043:Motor Activity; D010108:Oxyhemoglobins / Q000378:metabolism; D010953:Plasma Volume; D012083:Renin / Q000097:blood; D013997:Time Factors; D055815:Young Adult
chemical_list: D015415:Biomarkers; C554270:EPO protein, human; D010108:Oxyhemoglobins; D004921:Erythropoietin; D012083:Renin
keywords: Blood volume; confinement; hypovolemia; microgravity; renin