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Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude

KEY POINTS: Acclimatization to hypoxia leads to a reduction in plasma volume (PV) that restores arterial O(2) content. Findings from studies investigating the mechanisms underlying this PV contraction have been controversial, possibly as experimental conditions were inadequately controlled. We exami...

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Autores principales: Schlittler, Maja, Gatterer, Hannes, Turner, Rachel, Regli, Ivo B., Woyke, Simon, Strapazzon, Giacomo, Rasmussen, Peter, Kob, Michael, Mueller, Thomas, Goetze, Jens P., Maillard, Marc, van Hall, Gerrit, Feraille, Eric, Siebenmann, Christoph
Formato: Online Artículo Texto
Lenguaje:English
Publicado: John Wiley and Sons Inc. 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894546/
https://www.ncbi.nlm.nih.gov/pubmed/33124686
http://dx.doi.org/10.1113/JP280601
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author Schlittler, Maja
Gatterer, Hannes
Turner, Rachel
Regli, Ivo B.
Woyke, Simon
Strapazzon, Giacomo
Rasmussen, Peter
Kob, Michael
Mueller, Thomas
Goetze, Jens P.
Maillard, Marc
van Hall, Gerrit
Feraille, Eric
Siebenmann, Christoph
author_facet Schlittler, Maja
Gatterer, Hannes
Turner, Rachel
Regli, Ivo B.
Woyke, Simon
Strapazzon, Giacomo
Rasmussen, Peter
Kob, Michael
Mueller, Thomas
Goetze, Jens P.
Maillard, Marc
van Hall, Gerrit
Feraille, Eric
Siebenmann, Christoph
author_sort Schlittler, Maja
collection PubMed
description KEY POINTS: Acclimatization to hypoxia leads to a reduction in plasma volume (PV) that restores arterial O(2) content. Findings from studies investigating the mechanisms underlying this PV contraction have been controversial, possibly as experimental conditions were inadequately controlled. We examined the mechanisms underlying the PV contraction evoked by 4 days of exposure to hypobaric hypoxia (HH) in 11 healthy lowlanders, while strictly controlling water intake, diet, temperature and physical activity. Exposure to HH‐induced an ∼10% PV contraction that was accompanied by a reduction in total circulating protein mass, whereas diuretic fluid loss and total body water remained unchanged. Our data support an oncotically driven fluid redistribution from the intra‐ to the extravascular space, rather than fluid loss, as the mechanism underlying HH‐induced PV contraction. ABSTRACT: Extended hypoxic exposure reduces plasma volume (PV). The mechanisms underlying this effect are controversial, possibly as previous studies have been confounded by inconsistent experimental conditions. Here, we investigated the effect of hypobaric hypoxia (HH) on PV in a cross‐over study that strictly controlled for diet, water intake, physical activity and temperature. Eleven males completed two 4‐day sojourns in a hypobaric chamber, one in normoxia (NX) and one in HH equivalent to 3500 m altitude. PV, urine output, volume‐regulating hormones and plasma protein concentration were determined daily. Total body water (TBW) was determined at the end of both sojourns by deuterium dilution. Although PV was 8.1 ± 5.8% lower in HH than in NX after 24 h and remained ∼10% lower thereafter (all P < 0.002), no differences were detected in TBW (P = 0.17) or in 24 h urine volumes (all P > 0.23). Plasma renin activity and circulating aldosterone were suppressed in HH during the first half of the sojourn (all P < 0.05) but thereafter similar to NX, whereas no differences were detected for copeptin between sojourns (all P > 0.05). Markers for atrial natriuretic peptide were higher in HH than NX after 30 min (P = 0.001) but lower during the last 2 days (P < 0.001). While plasma protein concentration was similar between sojourns, total circulating protein mass (TCP) was reduced in HH at the same time points as PV (all P < 0.03). Despite transient hormonal changes favouring increased diuresis, HH did not enhance urine output. Instead, the maintained TBW and reduced TCP support an oncotically driven fluid redistribution into the extravascular compartment as the mechanism underlying PV contraction.
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spelling pubmed-78945462021-03-02 Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude Schlittler, Maja Gatterer, Hannes Turner, Rachel Regli, Ivo B. Woyke, Simon Strapazzon, Giacomo Rasmussen, Peter Kob, Michael Mueller, Thomas Goetze, Jens P. Maillard, Marc van Hall, Gerrit Feraille, Eric Siebenmann, Christoph J Physiol Cardiovascular KEY POINTS: Acclimatization to hypoxia leads to a reduction in plasma volume (PV) that restores arterial O(2) content. Findings from studies investigating the mechanisms underlying this PV contraction have been controversial, possibly as experimental conditions were inadequately controlled. We examined the mechanisms underlying the PV contraction evoked by 4 days of exposure to hypobaric hypoxia (HH) in 11 healthy lowlanders, while strictly controlling water intake, diet, temperature and physical activity. Exposure to HH‐induced an ∼10% PV contraction that was accompanied by a reduction in total circulating protein mass, whereas diuretic fluid loss and total body water remained unchanged. Our data support an oncotically driven fluid redistribution from the intra‐ to the extravascular space, rather than fluid loss, as the mechanism underlying HH‐induced PV contraction. ABSTRACT: Extended hypoxic exposure reduces plasma volume (PV). The mechanisms underlying this effect are controversial, possibly as previous studies have been confounded by inconsistent experimental conditions. Here, we investigated the effect of hypobaric hypoxia (HH) on PV in a cross‐over study that strictly controlled for diet, water intake, physical activity and temperature. Eleven males completed two 4‐day sojourns in a hypobaric chamber, one in normoxia (NX) and one in HH equivalent to 3500 m altitude. PV, urine output, volume‐regulating hormones and plasma protein concentration were determined daily. Total body water (TBW) was determined at the end of both sojourns by deuterium dilution. Although PV was 8.1 ± 5.8% lower in HH than in NX after 24 h and remained ∼10% lower thereafter (all P < 0.002), no differences were detected in TBW (P = 0.17) or in 24 h urine volumes (all P > 0.23). Plasma renin activity and circulating aldosterone were suppressed in HH during the first half of the sojourn (all P < 0.05) but thereafter similar to NX, whereas no differences were detected for copeptin between sojourns (all P > 0.05). Markers for atrial natriuretic peptide were higher in HH than NX after 30 min (P = 0.001) but lower during the last 2 days (P < 0.001). While plasma protein concentration was similar between sojourns, total circulating protein mass (TCP) was reduced in HH at the same time points as PV (all P < 0.03). Despite transient hormonal changes favouring increased diuresis, HH did not enhance urine output. Instead, the maintained TBW and reduced TCP support an oncotically driven fluid redistribution into the extravascular compartment as the mechanism underlying PV contraction. John Wiley and Sons Inc. 2020-11-16 2021-02-15 /pmc/articles/PMC7894546/ /pubmed/33124686 http://dx.doi.org/10.1113/JP280601 Text en © 2020 The Authors. The Journal of Physiology published by John Wiley & Sons Ltd on behalf of The Physiological Society. This is an open access article under the terms of the http://creativecommons.org/licenses/by/4.0/ License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
spellingShingle Cardiovascular
Schlittler, Maja
Gatterer, Hannes
Turner, Rachel
Regli, Ivo B.
Woyke, Simon
Strapazzon, Giacomo
Rasmussen, Peter
Kob, Michael
Mueller, Thomas
Goetze, Jens P.
Maillard, Marc
van Hall, Gerrit
Feraille, Eric
Siebenmann, Christoph
Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude
title Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude
title_full Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude
title_fullStr Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude
title_full_unstemmed Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude
title_short Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude
title_sort regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude
topic Cardiovascular
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7894546/
https://www.ncbi.nlm.nih.gov/pubmed/33124686
http://dx.doi.org/10.1113/JP280601
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