Related Experiment Videos
Long-term sodium balance in humans in a terrestrial space station simulation study
Jens Titze1, Alain Maillet, Rainer Lang
1Department of Physiology, Free University of Berlin, Germany. jus.titze@t-online.de
Summary
This study found that astronauts can gain significant body sodium without proportional weight gain, challenging the traditional view of sodium balance. This suggests a new osmotically inactive sodium reservoir may exist in the body.
Area of Science:
- Space Medicine
- Human Physiology
- Metabolic Studies
Background:
- Traditional view: Sodium accumulation increases extracellular volume and body weight.
- Recent studies: Sodium accumulation observed without extracellular volume expansion.
- This study: Investigates sodium balance and body weight (BW) during long-term isolation.
Purpose of the Study:
- To investigate sodium balance and its impact on body weight (BW) during a long-term balance study.
- To challenge the traditional view of sodium accumulation and its relation to extracellular volume.
Main Methods:
- Three healthy subjects confined to a terrestrial MIR simulator for 135 days.
- Simulated long-term spaceflight conditions.
- Daily measurement of sodium balance and its contribution to BW.
Main Results:
- Subjects accumulated 2,973–7,324 mmol of sodium and gained 5.1–9.3 kg.
- Positive correlation between total-body sodium (TBS) and BW, indicating sodium-associated volume expansion.
- Sodium gain exceeded weight gain, suggesting osmotically inactive sodium storage, especially towards the end of isolation.
Conclusions:
- Finding of sodium gain without weight gain contradicts established theories.
- Suggests the existence of a sodium reservoir storing sodium in an osmotically inactive form.
- Potential locations for this reservoir include bone, dense connective tissue, or cartilage.