Mg28 kinetics in man

Abstract

Following the intravenous injection of Mg28 to 15 normal adults on metabolic balance regimens, a multicompartmental-type analysis was used to describe the isotopic and metabolic data. The compartmental sizes and transfer constants were obtained with the NIH-OMR-SAAM program and an IBM 7094 computer. Only 15% of the estimated whole-body magnesium could be accounted for by rapid exchange processes with total body exchangeable magnesium averaging 3.54 meq/kg body weight. Two rapidly exchanging compartments when combined approximated extracellular fluid in distribution and a third, containing over 80% of the total exchangeable pool, reflected intracellular magnesium. The data also suggest the presence of another magnesium compartment accounting for most of whole-body magnesium which exchanges very slowly with an estimated biological half-life of 1,000 hr.