Study of Magnesium Absorption Using 25Mg Stable Isotope and Inductively Coupled Plasma/Mass Spectrometry Technique in Rat

Abstract

Magnesium metabolism is regulated at the intestine and kidneys by controlling the fraction of Mg absorbed from the total dietary intake and by renal homeostasis (1,2). As interest in Mg dietary requirements and metabolism has grown, the need for safe and convenient techniques for measurement of Mg absorption and bioavailability has increased. Balance studies are imprecise, labor intensive, give little information on Mg metabolism and do not consider the endogenous fecal excretion (3). Although kinetic analysis has been performed with the short-lived 28Mg radioisotope, the use of radio isotopes in humans is hazardous and restricts the experiment to a few days duration and is being supplanted by stable isotope methods (4). The use of extrinsic labeling presumes that the administered isotope behaves in the same way and that its absorption is the same as that of endogenous forms of Mg. The validity of the extrinsic labeling approach is now well established (5,6,7). Stable isotopes have been analyzed by two different analytical techniques; neutron activation and mass spectrometry. Although thermal ionization mass spectrometry (TIMS) is the reference technique, inductively coupled argon plasma mass spectrometry (ICP/MS) is also being widely developed (8). ICP/MS has many advantages in stable isotope measurement and has been applied to metabolic studies of many different minerals. In the present work, the feasibility of using a Mg stable isotope and ICP/MS technique to study Mg absorption and metabolism was explored in adult rats and the optimum dosage of the isotope was investigated.