title: Measurement of 47calcium retention with a whole-body counter.
abstract: A method for measuring the retention of orally administered 47Ca using a whole-body counter (WBC) is described. One microcurie 47Ca in 90 ml of lowfat milk was given along with 5 microCi 51Cr as a stool marker. The retention of 47Ca was determined at 7 days if less than 2% of the administered 51Cr was present in the body. Correlation between calcium retention by the whole-body-counting and the excreta-recovery methods was highly significant (r = 0.835, P less than 0.0001; N = 17). In 5 subjects, each studied twice while on constant self-selected diets, calcium retention was measured by the WBC method with a precision (standard deviation) of +/- 2.6% of the administered dose or +/- 13.9% of the mean retained fraction. Whole-body measurement of 47Ca retention has the advantages over other techniques that no collections of blood or stool are needed, no residency on a metabolic ward is required, and the radiation exposure (13 mrem) is so low that multiple studies may be performed in the same subject.
mesh_terms: D000042:Absorption; D000284:Administration, Oral; D000328:Adult; D000368:Aged; D002118:Calcium / Q000378:metabolism / Q000493:pharmacokinetics*; D002132:Calcium Radioisotopes; D005260:Female; D006801:Humans; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D014915:Whole-Body Counting / Q000379:methods*
chemical_list: D002132:Calcium Radioisotopes; D002118:Calcium