Multicompartmental analysis of calcium kinetics in normal adult males.

This report describes studies of calcium kinetics in ten normal young men. Serum, urinary, and fecal radioactivity was measured from 1 minute to 20 days after intravenous tracer (47)Ca injection, and these results were analyzed jointly with data obtained from a simultaneous metabolic balance study, using digital computer techniques. Surface radioactivity measurements were also obtained to gain further insight into the anatomic correlates of the tracer distribution. The data were satisfied by a model with four exchanging compartments. Series, branching, and mammillary models were analyzed. Several parameters of physiologic interest were independent of the model, but two were dependent on the duration of the study. Individual and mean values for these kinetic analyses are presented with their statistical uncertainties. These studies present detailed analyses in a healthy, normal population and provide a reference for future studies of skeletal metabolism and serum calcium homeostasis.