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Modeling Calcium Loss from Bones During Space FlightCalcium loss from bones during space flight creates a risk for astronauts who travel into space, and may prohibit space flights to other planets. The problem of calcium loss during space flight has been studied using animal models, bed rest (as a ground-based model), and humans in-flight. In-flight studies have typically documented bone loss by comparing bone mass before and after flight. To identify changes in metabolism leading to bone loss, we have performed kinetic studies using stable isotopes of calcium. Oral (Ca-43) and intravenous (Ca-46) tracers were administered to subjects (n=3), three-times before flight, once in-flight (after 110 days), and three times post-flight (on landing day, and 9 days and 3 months after flight). Samples of blood, saliva, urine, and feces were collected for up to 5 days after isotope administration, and were analyzed for tracer enrichment. Tracer data in tissues were analyzed using a compartmental model for calcium metabolism and the WinSAAM software. The model was used to: account for carryover of tracer between studies, fit data for all studies using the minimal number of changes between studies, and calculate calcium absorption, excretion, bone calcium deposition and bone calcium resorption. Results showed that fractional absorption decreased by 50% during flight and that bone resorption and urinary excretion increased by 50%. Results were supported by changes in biochemical markers of bone metabolism. Inflight bone loss of approximately 250 mg Ca/d resulted from decreased calcium absorption combined with increased bone resorption and excretion. Further studies will assess the time course of these changes during flight, and the effectiveness of countermeasures to mitigate flight-induced bone loss. The overall goal is to enable human travel beyond low-Earth orbit, and to allow for better understanding and treatment of bone diseases on Earth.
Document ID
20000084164
Acquisition Source
Johnson Space Center
Document Type
Preprint (Draft being sent to journal)
Authors
Wastney, Meryl E. (Georgetown Univ. Medical Center Washington, DC United States)
Morukov, Boris V. (Institute of Biomedical Problems Moscow, USSR)
Larina, Irina M. (Institute of Biomedical Problems Moscow, USSR)
Abrams, Steven A. (Baylor Coll. of Medicine Houston, TX United States)
Nillen, Jeannie L. (Enterprise Advisory Services, Inc. Houston, TX United States)
Davis-Street, Janis E. (Enterprise Advisory Services, Inc. Houston, TX United States)
Lane, Helen W. (NASA Johnson Space Center Houston, TX United States)
Smith, Scott M. (NASA Johnson Space Center Houston, TX United States)
Paloski, W. H.
Date Acquired
September 7, 2013
Publication Date
January 1, 1999
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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