Evaluation of body magnesium stores

517 47 3MB

English Pages 10 Year 1974

Report DMCA / Copyright

DOWNLOAD FILE

Polecaj historie

Evaluation of body magnesium stores

Citation preview

The Journal of LABORATORY and CLINICAL MEDICINE Copyright

VOLUME 84

© 1974

by The C. V. Mosby Company

AUGUST 1974

NUMBER 2

Clinical and experimental Evaluation of body magnesium stores ALLEN C. ALFREY, NANCY L. MILLER, and DONALD BUTKUS Denver, Colo.

Muscle, erythrocyte, and bone magnesium was studied in patients with reduced, normal, and increased serum magnesium levels. Muscle magnesium content was shown to vary directly with muscle potassium levels and independently of other body magnesium stores. In contrast to the fact that serum magnesium did not consistently reflect muscle magnesium concentration there was a highly significant correlation between serum and bone magnesium levels. It would appear from these results that bone and extracellular fluid magnesium are the major magnesium pools in man increased dlJring magnesium excess and decreased during magnesium depletion. Changes in muscle magnesium reflect changes in total body potassium and are not a valid indicator of total body magnesium.

Rasma, erythrocyte, muscle, and bone magnesium levels have all been used to estimate total body magnesium stores. During experimentally induced magnesium depletion the first change appears to be a fall in serum magnesium concentration. 1 However, recent studies by Lim and Jacobs 2 - 4 have shown reduced muscle magnesium in association with normal serum, erythrocyte, and bone magnesium levels in patients with chronic renal insufficiency, cirrhosis, and chronic diarrhea. The above authors have suggested that muscle magnesium is the most freely exchangeable and thus the first to fall during magnesium depletion. In contrast, Dunn and Walsers in experimentally induced magnesium From the Veterans Administration Hospital and University of Colorado Medical Center, Denver. This study was supported in part by a grant from the Veterans Administration and by a grant (RR-51) from the General Clinical Research Centers, National Institutes of Health. Received for publication Nov. 5, 1973. Accepted for publication May 2, 1974. Reprint requests: Dr. Allen C. Alfrey, Chief, Renal Medicine, Veterans Administration Hospital, 1055 Clermont St., Denver, Colo. 80220.

153

154 illfrey, Miller, and Butkus

]. Lab. Clin. Med August. 1974

3 5

,/

3.0

~o

2.5 UL TRAFILTERABLE MAGNESIUM

0/ 0

2·0

0

mEq/L

1.5 1.0

0 0

.5 ,=0.99 UF Mg =0.78(10'01 Mg)'.OI o~--~--~--.---.---.---.---.---~

o

.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

SERUM MAGNESIUM

mEq/l

Fig. 1. Correlation between total serum magnesium and ultrafiltrable magnesium.

Table I. Blood and tissue values in control subjects Mean ± 1 S.D.

No. Serum Mg Ultrafiltrable Mg Erythrocyte Mg Muscle Mg Muscle K Muscle Ca Cortical bone Mg

(31) (22) (27) (8) (8) (8) (6)

• 1.56 ± 1.15 4.60 75.6 424 12.6 352

± ± ± ± ± ±

0.08 0.05 0.34 8.6 28 5.2 20

mEq./L. mEq./L. mEq./L. mEq./Kg. mEq./Kg. mEq./Kg. mEq./Kg.

FFDS FFDS FFDS Ash

depletion and Muldowney and associates 6 in patients with malabsorption syndrome found reduced serum magnesium levels in association with normal muscle magnesium content. Although bone contains approximately 65 per cent of the total body magnesium and has usually been found to be decreased in experimentally induced magnesium depletion in animals, bone magnesium has rarely been measured in hypomagnesemic patients. Even fewer studies have been carried out in patients with hypermagnesemia to determine whether the elevated serum magnesium concentration is associated with increased magnesium content of other body pools. The purpose of the present study is to correlate serum, erythrocyte, bone and muscle magnesium levels in patients with hypo- and hypermagnesemia and to determine what effect alterations in other intracellular cations have on muscle magnesium levels. Methods Normal values for serum, ultrafiltrable, and erythrocyte magnesium were obtained from blOod donors and members of a hemodialysis ;taff. The normal values for muscle and bone magnesium were obtained from nonhospitalized patients who experienced sudden death (U~u~lly auto accident victims). The study group consisted of renal transplant donors and recipIents, patients with chronic renal failure, renal tubular acidosis, magnesium· losing

\ 'olume

Body magnesium stm'es

8~

'umber .2

155

4 ,0

3 ,0

PLASMA MAGNESIUM

2,0

mEq/L

1.0

r -069 O+---~---r---'--__r---~--~---.---'

2

3

4

5

6

7

8

9

REO CELL MAGNESIUM mEq/L

Fig. £. Correlation between serum and erythrocyte magnesium levels. The normal range for erythrocyte and serum magnesium is shown by the rectangle. The open circles represent patients with chronic renal failure and the closed circles patients with a variety of disorders of magnesium and potassium m~tabolism.

nephropathy, prima ry hyperaldoateronism, hypokalemia secondary to laxative abuse, and chronic alcoholism. Informed consent was obtained from all patients from whom blood or tissue samples were taken for this study. Heparinized blood was centrifuged at 2,000 r.p.m. for 10 minutes immediately following withdrawal. The plasma was removed for analysis and ultrafiltrable magnesium was determined by the method of Lavietes 7 under strict anaerobic conditions. The red blood cells were transferred to a 150 mm. by 1.5 mm. (intemal diameter) capillary tube and recentrifuged for 2 hours at 2,000 r.p.m. in It refrigerated centrifuge. The tubes were broken 1 to 2 mm. below the buffy coat to obtain the packed r ed blood cells. Muscle and bone were obtained both at autopsy and by surgical biopsy. Bone was uniformly taken from the iliac crest. ; wll('r