Annotations

Magnesium and the Cardiovascular System

Interest in the role of magnesium in the cardio\xcular system was first stimulated by the work of &use and associates,’ Sjollema,2 and Greenberg and ‘1‘ufts,a who demonstrated the oc- currence of cardiac necrosis, fibrosis and calcification, vascular dilatation and nephrocalcinosis in the weanling rat fed a magnesium-deficient diet. SubsequentI>., similar lesions were produced by a magnesium-deficient diet in a variety of experimental animals.

Recent experimental studies in animals ha\,e been centered about the interrelationships between atherosclerosis, magnesium, and thyrosine. \‘itale and his group”-6 have shown that fecd- ing atherogenic diets to weanling rats caused deposition of lipid in aorta and heart valx.es. Large amounts of dietary magnesium reduced this vascular sudanophilia. even though the levels of serum cholesterol rose. Administration of thJ,roxine to rats on an athcrogenic diet decreased the levels of serum cholesterol, abolished the nephrocalcinosis, and reduced the intimal sudanophilia, even though the levels of serum magnesium remained low. Furthermore, these inl-estigators found that adding atherogenic agents (cholesterol and cholic acid) to a diet containing 24 mg. per cent magnesium (enough for the normal requirement) produced typical symptoms and findings of magnesium deficiency. All symptoms and lesions were prevented by markedly raising the level of the dietary magnesium. Both in the rat with a low level of serum magnesium following use of an atherogenic diet, and after the feeding of thyro,xinc a decreased efficiency of 0xidatiL.e phos- phorylation of heart muscle mitochondria occurred. It has been established for several !-ears that all ATP-catalyzed reactions have an absolute requirement for magnesium.~ Furthermore, this groups has shown that an atherogenic diet given to weanling rat. 5, with 20 per rent ;tlcohol ;LS the drinking fluid, produced higher levels of serum cholesterol and more deposits of lipid than when water was used. High levels of dietar)- magnesium lowered the amount of lipid deposited. .Ucohol increased the requirement for magnesium in the basic diet, as did the addition of atherogenic agents.

A profound influence of the intake of protein on the requirement for magnesium haa also been demonstrated in the rat,g because protein-depleted rats on a magnesium-deficient diet gained two times as much when the diet contained 7 per cent protein, as when the diet contained 14 pet cent protein, in contrast to these diets with an adequate lel-el of magllesium.

Studies with isotopic magnesium (Mg’*) in dogs has shown that the concentration of bIgz8 was higher in the tissue of the heart than in an)- other tissue, and that this was Ilot related to blood flow or muscle contraction.‘0

Cardiac necrosis has been produced in rats by the use of NaIl?l’04 plus a steroid (Me-CI- Co&AC), with marked decrease in the level of cardiac magnesium, and increase in the level of sodium and calcium.” It was ihought that the cardiac lesions were due to low levels of cardiac magnesium. Myocardial infarct-like lesions and atherosclerosis were produced by other \vorkerhLz through the use of substances of high-molecular weight. ‘fhe lesions were prc\.ented b!, the use of magnesium salts.

The work on magnesium in animals cannot, to date, be transferred directly to man. As for magnesium studies in man, it has been shown that, with aging, there is an increase in the content of calcium and magnesium in the human aorta. 13 A recent study showed higher than normal lex.els

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ANNOTATIONS

of serum magnesium and lower levels of cholesterol in the Bantu, as compared to the European. ;\ possible inverse relationship between the Icx-el of serum magnesium and the level of serlml ch(;lesterol was suggested, because the Bantu has very little coronary artery disease.”

The relationship of magnesium to clinical hypertension has been studied in a few p;ltienty with uncomplicated hypertension. ‘l‘he Ic\ els of serum magnesium were significantly lower, an(l the levels of serum sodium were higher, than in controls.‘” It was thought that this might represcllt increased adrenal cortical arti\-ity similar to that seen in primar)- aldosteronis~n, in which hype- magnesemia may occur. ;\ magtlesium-de~ciellt diet in man ha> led to a transient loss of potassium, and retention of sodium and chloride.“;

Helen Martin, M.1). Los I\ngeles, Calif.

1. K-use, H. I)., Orent, E. R., and 1lcCollum, E. V.: Studies on Magnesium Deficiency in Animals. I. Symptomatology Resulting From Rlngnesium Deprivation, J. Hiol. Chcm. 96:519, 1932.

2. Sjollema, B.: Nutritional and ikletabolic I)isorders in Cattle, Nlltrition Abst. and Rev. 1:621, 1932.

3. Greenberg, I). IV., and Tufts, E. V.: The Nature of hlagnesium Ijeficiency, Am. J. I’hysiol. 121:116, 1938.

4. Vitale, J. J., LfThite, P. L., Nakamura, XI., Hegsted, D. hr., Zamchcck, N., and Hellerstein, E. E.: Interrelationships Between Experimental Hypercholcsteremia, Magnesium Requirement and Experimental Atherosclerosis, J. Esper. XIed. 106:757, 1957.

5. llellerstein, E. E., Vitale, J. J., \Vhite, I’. L., Hegsted, D. M., Zamcheck, N., and Nakamura, %I.: Influence of Dietary Magnesium on Cardiac and Renal Lesions of Young Rats Fed an Atherogenic Diet. J. Esper. Med. 106:767, 1957.

6. Vitale, J. J., Nakamura, M., Connors, P., and Hegsted, I’. M.: The Eifect of Thyrosille

7. on Magnesium Requirement, J. Biol. Chem. 226:59!, 1957.

Colowick, S. P.: b2ethods in Enzymology, Vol. 2, New \1 ark, 1951, .\cademic Press, Inc., pp. 598-616.

8. Gottlieh, L. S., Broitman, S. AA., \:itale, J. J., and Zatncheck, N.: The Influence of Alcohol and Dietary Magnesium ITpon HTpercholesterolernia and Atherogenesis in the Rat, J. Lab. & Clin. Med. 53:433, 1959.

9. Rlenaker, W.: Influence of Protein Intake on Magnesium Requirement During Protein Synthesis, Proc. Sot. Esper. Med. & Biol. 85:149, 19%

10. Brandt, J. L., Glaser, W., and Jones, A.: Soft Tissue Distribution and Plasma Disappearance of Intravenously Administered Isotopic XIagnesium, With Obser\-ations on I.ptake in Bone, Metabolism 7:355, 1958.

11. DuRuisseau, J. P., and bIori, K.: Biochemical Studies on Espcrimental Cardiopathy: Elec- trolytes in Rat Tissues, Brit. J. Esper. Path. 40:250. 1959.

12. Shimamoto, T., Fugita, T., and Shimura, H., Yamazake, H., Iwahara, S., and Yajima. G.: Llyocardial Infarct-Like Lesions and Arteriosclerosis Induced by High Molecular Substances and Prevention bv iMagnesium Salt, AM. HEART j. 57:273, 1959.

l.?. ;Lliller, H., Hirschman, A., and Kpaemcr, D. RI.: Calcium and Magnesium Content of i\l- buminoid Fraction of Human Aorta, A.M.r\. Arch. Path. 56:607, 1953.

14. Bersohn, I., and Oelope, I’. J.: Correlation of Serul71-nIagtlesillm and SeruIn-Cholesterol Ixvels in South African Bantu and European Subjects, Lancet 272:1020, 1957.

1.5. Albert, D. G., Morita, Y., and Iseri, L. ‘I’.: Serum Magnesium and Plasma Sodium Levels in Essential l’ascular Hypertension, Circulation 17:761, 19.58.

16. Fitzgerald, M. G., and Fourman, l’.: An Experimental Study of hlagncsium Deiicicncy in hIan, Clin. SC. 15:635, 1956.

Diagnostic Carbon Dioxide: Its Use in Review

It has been recognized for at least 40 )-ears that injections of air or oxygen into the body can be of appreciable diagnostic or therapeutic \.alue. Especially important examples of this are the diagnosis of adrenal tumors by perirenal or presncral injection of gas, intrauterine insufflation for diagnostic and therapeutic purposes, and the indurtion of pneumoperitoneum and pncumo- thorax. Progress along these lines has been seriously impeded by the occurrewe from time to time of fatal, or nearly fatal, accidents due to the inadvertent entrance of gas into the circulatory sys-