Measurement of Exchangeable Magnesium in Dogs

Journal/Book: METABOLISM VOL. 12 NO. 2 FEBRUARY 1963. 1962/1963;

Abstract: This study was supported by Grant A-1849-C3 from the National lnstitute of Arthritis and Metabolic Diseases and by Grant M-1955 from the National Institute of Mental Health of the National Institutes of Health United States Public Health Service and by Grant AT(30-1)2092 from the Atomic Energy Commission. Received for publication Nov. 15 1962. Benjamin A. Barnes M.D. Clinical Assaciate in Surgery Harvard Medical School and Assistant Surgean Massachusetts General Hospital Boston Massachusetts. Jack Mendelson M.D. Associate in Psychiatry Harvard Medical School and Assistant in Psychiatry Massachusetts General Hospital Boston Massachusetts. The meaning of exchangeable magnesium measurements as an Index of total body magnesium was assessed in 2 groups of dogs an a magnesium-free diet and a control diet for 9 weeks. The exchangeable magnesium determined at the 19th hour following Mg28 injection was compared to total carcass magnesium determined by a titan yellow dye method completed on a hydrochloric acid digestion of the carcass. In the control group the exchangeable magnesium was 7 mEq. per Kg. body weight and less than 16 mEq. obtained by total carcass analysis. The depletion caused by the experimental diet resulted in a serum magnesium of 0.8 mEq. per L. and an exchangeable magnesium of 4 mEq. per Kg. body weight. Carcass and tissue analysis established that the soft tissue magnesium is conserved and the bone magnesium is depleted during a magnesium-free diet. It is concluded that skeletal magnesium functions as a mineral reserve that the soft tissue magnesium is preferentially conserved and that the labile magnesium stores measured by the isotope are proportion ately more readily depleted than the magnesium determined by total carcass analysis.

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