title: Using natural, stable calcium isotopes of human blood to detect and monitor changes in bone mineral balance.
abstract: We are exploring variations in the Ca isotope composition of blood and urine as a new tool for early diagnosis and monitoring of changes in bone mineral balance for patients suffering from metabolic bone disease, cancers that originate in or metastasize to bone, and for astronauts who spend time in low gravity environments. Blood samples are often collected instead of, or in addition to, urine in clinical settings, so it is useful to know if variations in the Ca isotope composition of blood carry the same information as variations in urine. We found that the Ca isotope composition of blood shifts in the same direction and to the same magnitude (~2 parts per ten thousand--pptt) as that of urine in response to skeletal unloading during bed rest. However, the Ca isotope composition of blood is lighter than that of urine by 12 ± 2 pptt. This offset between blood and urine may result from Ca isotope fractionation occurring in the kidneys. This is the first study to confirm the suspected offset between the Ca isotope composition of blood and urine in humans, to directly quantify its magnitude, and to establish that either blood or urine can be used to detect and quantify bone loss.
authors.affiliation: School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA. Electronic address: mchannon@gmail.com.
authors.forename: Melanie B
authors.initials: MB
authors.lastname: Channon
authors.affiliation: School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA.
authors.forename: Gwyneth W
authors.initials: GW
authors.lastname: Gordon
authors.affiliation: Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, TX 77058, USA.
authors.forename: Jennifer L L
authors.initials: JL
authors.lastname: Morgan
authors.affiliation: L'Etoile, Madison, WI 43703, USA.
authors.forename: Joseph L
authors.initials: JL
authors.lastname: Skulan
authors.affiliation: Biomedical Research and Environmental Sciences Division, NASA Johnson Space Center, Houston, TX 77058, USA.
authors.forename: Scott M
authors.initials: SM
authors.lastname: Smith
authors.affiliation: School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287, USA; Department of Chemistry and Biochemistry, Arizona State University, Tempe, AZ 85287, USA.
authors.forename: Ariel D
authors.initials: AD
authors.lastname: Anbar
mesh_terms: D000328:Adult; D015519:Bone Density; D002127:Calcium Isotopes / Q000097:blood*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D002127:Calcium Isotopes
keywords: Biomarkers; Bone loss; Calcium; Isotopes