Dissimilar distribution of calcium isotopes in blood serum and urine

Abstract

A study of the distribution of tracer doses of radiocalcium 47 in blood serum and urine for 5 days after its intravenous administration to human subjects is presented. Using atomic absorption spectroscopy to determine total calcium, the specific activity of the urinary calcium 47 was found to be higher than that of the contemporary serum during the first 96 hr. Calculated renal clearance of calcium 47 was higher than that of calcium 40 during this time interval. Equilibrium dialysis of the serum resulted in a decrease in its calcium 47 specific activity, an effect which was enhanced by increasing the volume of dialyzing fluid. Fractions of serum collected from a Sephadex column contained unequal proportions of the two isotopes. The nonultrafiltrable calcium fractions appear to be heterogenous, and of different dissociation characteristics. At least one is not readily exchangeable with the diffusible calcium. renal clearance of calcium isotopes; metabolism of radiocalcium 47; distribution of calcium 47 in blood serum fractions; dialyzable serum calcium 47; serum calcium 47 specific activity; urine calcium 47 specific activity; nondialyzable serum calcium 47; calcium in Sephadex serum fractions Submitted on July 24, 1964