PlanHab: Hypoxia counteracts the erythropoietin suppression, but seems to exaggerate the plasma volume reduction induced by 3 weeks of bed rest. Issue 7 (13th April 2016)

• Record Type: Journal Article
• Authors: Keramidas, Michail E.; Mekjavic, Igor B.; Kölegård, Roger; Choukèr, Alexander; Strewe, Claudia; Eiken, Ola
• Is Part Of: Physiological reports. Volume 4:Issue 7(2016:Apr.)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2016-04-13
• Subjects: Blood volume -- confinement -- hypovolemia -- microgravity -- renin; Physiology -- Periodicals; 571
• DOI: 10.14814/phy2.12760
• Languages: English
• ISSNs: 2051-817X

Abstract

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; PI O2 : 133.1 ± 0.3 mmHg); (2) hypoxic bed rest (HBR; PI O2 : 90.0 ± 0.4 mmHg, ambient simulated altitude of ~4000 m); and (3) hypoxic ambulation (HAMB; PI O2 : 90.0 ± 0.4 mmHg). Blood samples were collected before, during (days 2, 5, 14, and 21) and 2 days after each confinement to determine EPO concentration. Qualitative differences in PV changes were also estimated by changes in hematocrit and hemoglobin concentration along with concomitant changes in plasma renin concentration. NBR caused an initial reduction in EPO by ~39% ( P = 0.04). By contrast, HBR enhanced EPO ( P = 0.001), but the increase was less than that induced by HAMB ( P < 0.01). All three confinements caused a significant reduction in PV ( P < 0.05), with a substantially greater drop in HBR than in the other conditions ( P < 0.001). Thus, present results suggest that hypoxia prevents the EPO suppression, whereas it seems to exaggerate the PV reduction induced by bed rest. Abstract : Hypoxia reverted the suppression of serum erythropoietin concentration caused by 3 weeks of horizontal bed rest in male lowlanders. However, based on the changes in hemoglobin concentration and hematocrit, and on the concomitant changes in renin concentration, it appears that the hypoxic stimulus might exaggerate the bed rest‐induced reduction in plasma volume.