Measurement of super(47)Calcium retention with a whole-body counter

A method for measuring the retention of orally administered super(47)Ca using a whole-body counter (WBC) is described. One microcurie super(47)Ca in 90 ml of lowfat milk was given along with 5 mu Ci super(51)Cr as a stool marker. The retention of super(47)Ca was determined at 7 days if less than 2% of the administered super(51)Cr was present in the body. Correlation between calcium retention by the whole-body-counting and the excreta-recovery methods was highly significant. 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 plus or minus 2.6% of the administered dose or plus or minus 13.9% of the mean retained fraction.