<?xml version='1.0' encoding='utf-8'?>
<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>T. Bullen</dc:contributor>
  <dc:contributor>A.D. Anbar</dc:contributor>
  <dc:contributor>J.E. Puzas</dc:contributor>
  <dc:contributor>L. Shackelford</dc:contributor>
  <dc:contributor>A. LeBlanc</dc:contributor>
  <dc:contributor>S. M. Smith</dc:contributor>
  <dc:creator>J. Skulan</dc:creator>
  <dc:date>2007</dc:date>
  <dc:description>Background: We investigated whether changes in the natural isotopic composition of calcium in human urine track changes in net bone mineral balance, as predicted by a model of calcium isotopic behavior in vertebrates. If so, isotopic analysis of natural urine or blood calcium could be used to monitor short-term changes in bone mineral balance that cannot be detected with other techniques. Methods: Calcium isotopic compositions are expressed as ??44Ca, or the difference in parts per thousand between the 44Ca/40Ca of a sample and the 44Ca/ 40Ca of a standard reference material. ??44Ca was measured in urine samples from 10 persons who participated in a study of the effectiveness of countermeasures to bone loss in spaceflight, in which 17 weeks of bed rest was used to induce bone loss. Study participants were assigned to 1 of 3 treatment groups: controls received no treatment, one treatment group received alendronate, and another group performed resistive exercise. Measurements were made on urine samples collected before, at 2 or 3 points during, and after bed rest. Results: Urine ??44Ca values during bed rest were lower in controls than in individuals treated with alendronate (P &lt;0.05, ANOVA) or exercise (P &lt;0.05), and lower than the control group baseline (P &lt;0.05, Mest). Results were consistent with the model and with biochemical and bone mineral density data. Conclusion: Results confirm the predicted relationship between bone mineral balance and calcium isotopes, suggesting that calcium isotopic analysis of urine might be refined into a clinical and research tool. ?? 2007 American Association for Clinical Chemistry.</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1373/clinchem.2006.080143</dc:identifier>
  <dc:language>en</dc:language>
  <dc:title>Natural calcium isotonic composition of urine as a marker of bone mineral balance</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>