CLINICAL SCIENCES INVESTIGATIVE NUCLEAR MEDICINE Effects of Dietary Magnesium Deficiency on Thallium-201 Kinetics and Distribution in Rat Myocardium: Concise Communication

Kinetics and distribution of TI-201 were studied In myocardium of rats with chronic dietary induced Mg deficiency. Rats were fed the Mg-deficient diet for 30 days and were then Injected intravenously with 0.2 mCl of TI-201. Comparable control animals were fed a standard laboratory diet. One-half hour after injection, rats were killed and a segment of myocardium was washed with nonradioactive Krebs solution in a special chamber. Radioactivity in the tissue was recorded con tinuously for 1 hr. A three-compartment model (extracellular, main intracellular, and subcellular) was found to describe adequately the kinetics of TI-201. In myo cardium of Mg-deficient animals, significant changes in values of transport rate constants and compartment sizes for TI-201 indicated a moderate decrease in ex tracellular compartment and a threefold enlargement in subcellular compartment (presumably mitochondrial) at the expense of the main intracellular compartment, which underwent a marked reduction. Bulk TI-201 uptake in myocardium of Mg-deficient rats was unchanged. The findings are interpreted as being consistent with mitochondrial alterations reported in Mg-deficient animals. Clinical implication