Magnesium metabolism in human beings: studies with Mg²⁸

Abstract

Mg28 was used to explore the kinetics of magnesium distribution in 9 normal individuals and in 16 patients with various diseases. When Mg28 was given in 12–30 mEq of stable magnesium intravenously, plasma disappearance was rapid within the first several hours. In normal subjects a mean of 19.8% of the injected radioactivity was accounted for in the urine within 24 hours. Fecal excretion was negligible, although equilibration of Mg28 in bile occurred within 18 hours. The specific activities of plasma and urine stabilized by the 18th hour, and showed only a gradual decrease thereafter. Exchangeable magnesium contents in normal subjects ranged between 2.6 and 5.3 mEq/kg of body weight—less than 16% of the estimated total body content of magnesium. Mg28 exchanged very slowly with the stable ion in bone, muscle and erythrocytes. The results in patients with diabetes mellitus and hepatic diseases showed no striking differences from those obtained in normal subjects. Note: (With the Technical Assistance of Dale R. Harms and Jacqueline Z. Reardon) Submitted on October 5, 1959

The Relationship Between Magnesium and Calcium Kinetics in 9- to 14-Year-Old Children

“…There are minimal previous data regarding Mg kinetics in humans (7,8,12‐14) . The Mg exchangeable pool size (Mg comp ) reported in this study averaged 49 mg/kg, which is similar to previous results in adults (7,17) .…”

“…Previous studies using radioactive tracers have shown that Mg distribution occurs throughout the extracellular fluid during the initial hours after infusion, with subsequent distribution to separate compartments segregated from the extracellular fluid. Some component of the exchangeable Mg probably includes bone, although the exact size of this contribution is not readily measured (7,17,19) . We found evidence that this bone component is small by the ratio of Mg comp /Ca comp .…”

Production of carrier-free 28Mg by 50--200 MeV protons on natCl: excitation function and target optimization

“…This is shown in figure 4 for LiCl targets ranging in thickness from 2 g/cm 2 to 32 g/cm 2 . It is clear that, regardless of the target thickness, the highest yield is always obtained with the highest incident proton energy.…”

“…Since its introduction circa 1952 as a radiotracer in biochemical studies [1], 28 Mg found wide application in the study of absorption, retention and excretion in metabolic processes in animals and humans [2][3][4]. Magnesium is the second most abundant soft tissue intracellular cation in vertebrates and an essential nutrient for all living organisms.…”

Untitled

“…Only 23% of MgTB (15 mmol kg-') exchanges with administered Mg isotope after 120 h and most of this is in tissues other than muscle or bone [31,54,55]. Given the relatively large variation from subject to subject, the short half-life (21.4 [4,47,56].…”