SOdium LOading in Microgravity (SOLO) - 10.28.15

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ISS Science for Everyone

Science Objectives for Everyone
SOdium LOading in Microgravity (SOLO) studies the mechanisms of fluid and salt retention in the body during space flight.
Science Results for Everyone
Information Pending

The following content was provided by Martina A. Heer, Ph.D., and is maintained in a database by the ISS Program Science Office.
Information provided courtesy of the Erasmus Experiment Archive.
Experiment Details


Principal Investigator(s)
Martina A. Heer, Ph.D., University of Bonn, Bonn, Germany

Natalie Baecker, Institute of Aerospace Medicine, Cologne, Germany
Petra Frings-Meuthen, Institute of Aerospace Medicine, Cologne, Germany
Peter Norsk, M.D., University of Copenhagen, Copenhagen, Denmark

Information Pending

Sponsoring Space Agency
European Space Agency (ESA)

Sponsoring Organization
Information Pending

Research Benefits
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ISS Expedition Duration 1
April 2008 - October 2009; March 2010 - September 2012

Expeditions Assigned

Previous ISS Missions
SOLO was first operated on ISS Expedition 17.

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Experiment Description

Research Overview

  • Microgravity leads to an activation of sodium retaining hormones even at normal sodium intake levels and causes positive sodium balances. Average and high sodium intake in microgravity exacerbates the rise in bone resorption in space.

  • SOdium LOading in Microgravity (SOLO) is a continuation of extensive research into the mechanisms of fluid and salt retention in the body during bed rest and space flights; It is a metabolically controlled study.

  • During long-term space missions crewmembers will participate in two study phases, 5 days each. Subjects follow a diet of constant either low or normal sodium intake and increased fluid consumption.

The hypothesis of an increased urine flow as the main cause for body mass decrease has been questioned in several recently flown missions. Data from the American SLS1/2 missions as well as the European Euromir `94 and MIR 97 mission show that urine flow and total body fluid is unchanged when isocaloric energy intake is achieved.

However, in two astronauts during these missions the renin-angiotensin system was considerably activated while plasma ANP concentrations were decreased. Calculation of daily sodium balances during a 15 day experiment of the MIR 97 mission, by subtracting sodium excretion from sodium intake- showed an astonishing result: the astronaut retained on average 50 mmol sodium daily in space compared to balanced sodium in the control experiment.

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Space Applications
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Earth Applications
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Operational Requirements
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Operational Protocols
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Decadal Survey Recommendations

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Results/More Information

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Results Publications

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Ground Based Results Publications

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ISS Patents

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Related Publications

    Heer MA, Frings-Meuthen P, Titze J, Boschmann M, Frisch S, Baecker N, Beck L.  Increasing sodium intake from a previous low or high intake affects water, electrolyte and acid-base balance differently. British Journal of Nutrition    . 2009 May; 101(9): 1286-1294. DOI: 10.1017/S0007114508088041. PMID: 19173770.

    Frings-Meuthen P, Baecker N, Heer MA.  Low-grade metabolic acidosis may be the cause of sodium chloride-induced exaggerated bone resorption. Journal of Bone and Mineral Research. 2008 April; 23(4): 517-524. DOI: 10.1359/jbmr.071118. PMID: 18052757.

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Related Websites
The information on this page is provided courtesy of the ESA Erasmus Experiment Archive.

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image NASA Image: ISS017E018995 - Astronaut Greg Chamitoff, Expedition 17 Flight Engineer (FE) in the Kibo European Laboratory/Columbus. The Space Linear Acceleration Mass Measurement Device (SLAMMD) is visible on the left of frame.
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