Original Investigations: Pathogenesis and Treatment of Kidney Disease and HypertensionLong-term sodium balance in humans in a terrestrial space station simulation study*,**,★,★★
Section snippets
Subjects and environmental conditions
During HUBES, three male subjects were isolated over a period of 135 days. Two subjects (no. 002 and 003) were trained cosmonauts, and successful participation in the isolation study would qualify them for a space flight. According to body mass index, subject 004 was marginally underweight, whereas subjects 002 and 003 were of normal body mass index (Table 1).
The isolation study was conducted at the Institute for Biomedical Problems in Moscow and approved by several ethical boards of the
BW and body composition
Figure 1 shows changes in BW over the entire isolation period. Descriptives are listed in Table 1. BW increased substantially in all subjects, at least initially, but eventually tended to remain stable in all subjects. Figure 2 shows changes in body composition.
Discussion
We determined long-term sodium balances to investigate whether infradian oscillations in TBS content exist in humans. In addition to such hypothetical oscillations, subjects showed an unexpected excessive sodium accumulation. TBS content in humans is estimated at 55 to 60 mmol/kg BW.14, 15 If this held true, sodium accumulation in subject 004 almost tripled his TBS content from presumed normal values to far beyond the norm. Excessive positive sodium balances toward the end of isolation give
Acknowledgements
The authors thank the three confined crew members for their cooperation during confinement, training, and control periods; R. Ziegler, for curve fitting; J. Nurrish-Weiß, for help with the text; and F.C. Luft, for advice and comments on the manuscript.
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This experiment was performed in the MIR simulator of the Institute for Biomedical Problems, Moscow, Russia.
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Supported in part by the European Space Agency-Long Term Program Office; and Else Kröner-Fresenius-Stiftung (J.T.). The Institute of Physiology, Free University of Berlin, receives financial support from DLR Germany, grant no. 50WB9622; and the Laboratory of Environmental Physiology (Lyon, France) receives financial support from CNES and GIP Exercise for its space-related research.
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Address reprint requests to Jens Titze, MD, Department of Nephrology, Friedrich-Alexander-University Erlangen-Nürnberg, Loschgestraße 8, 91054 Erlangen, Germany. E-mail: [email protected]
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