Studies on the Interrelationships Between Dietary Magnesium and Calcium in Atherogenesis and Renal Lesions

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Abstract
The variables involved in these studies with weanling rats were the level of dietary magnesium and dietary calcium and the presence or absence of the hypercholesterolemic agents, cholesterol or cholic acid. Measurements were made of growth, serum cholesterol, vascular sudanophilia (heart score), calcification in the kidney tubules (kidney score), kidney weights, and, in some groups, measurement of the serum proteins and lipoproteins. In hypercholesterolemic animals, additional magnesium invariably decreased the heart score in the animals receiving 600 or 1200 mg per 100 g dietary calcium. This effect was not related to changes in the serum cholesterol level. Magnesium was ineffective in decreasing the heart score in animals fed the lowest level of calcium, 200 mg per 100 g. Thus, it is concluded that some minimal level of calcium (above 200 mg per 100 g) must be fed for magnesium to be effective in diminishing vascular sudanophilia. Renal calcification was abolished by raising the level of dietary magnesium and may be independent of the presence or absence of hypercholesterolemic agents. In the animals fed the cholesterol-cholic acid-free diets, additional magnesium resulted in lower levels of both the alpha and beta lipoproteins. While this effect could not be shown in the hypercholesterolemic animals, it is possible that the effect on vascular sudanophilia may be mediated through the serum lipoproteins. Serum albumin was consistently decreased and the alpha and beta globulins increased in animals fed cholesterol and cholic acid. Additional magnesium tended to decrease the latter. The effects of dietary calcium are less clear. In confirmation of data in the literature and our previous studies, high levels of dietary calcium were usually detrimental to growth on low-magnesium diets and in two experiments intensified the kidney lesions. No specific effect of calcium upon the susceptibility of the vascular system to the deposition of lipid is apparent from these studies. However, unexpectedly high levels of serum cholesterol were observed in animals fed low-calcium diets containing no hypercholesterolemic agents.