Magnesium Metabolism in Health and Disease. I. The Magnesium and Calcium Excretion of Normal Individuals, Also the Effects of Magnesium, Chloride, and Phosphate Ions

257

152

The purpose of this study was to measure magnesium absorption over the wide range of intakes to which the intestine may be exposed from food and/or magnesium-containing medications. Net magnesium absorption was measured in normal subjects after they ingested a standard meal supplemented with 0, 10, 20, 40, and 80 mEq of magnesium acetate. Although absorption increased with each increment in intake, fractional magnesium absorption fell progressively (from 65% at the lowest to 11% at the highest intake) so that absorption as a function of intake was curvilinear. This absorption-intake relationship was almost perfectly represented by an equation containing a hyperbolic function plus a linear function. Our results are statistically compatible with a magnesium absorption process that simultaneously uses a mechanism that reaches an absorptive maximum, plus a mechanism that endlessly absorbs a defined fraction (7%) of ingested magnesium. Compared to previous studies of calcium absorption, much less magnesium than calcium was absorbed at intakes above 8 mEq/meal, apparently due to greater restriction of intestinal permeability to magnesium. We also found that magnesium from a high magnesiumcontaining food source, almonds, was just as bioavailable as from soluble magnesium acetate. In contrast, magnesium absorption from commercially available enteric-coated magnesium chloride was much less than from magnesium acetate, suggesting that enteric coating can impair magnesium bioavailability. (J. Clin. Invest. 1991.88:396-402.)

Section: Resultssupporting

confidence: 72%

Intestinal absorption of magnesium from food and supplements.

Fine¹,

Ana²,

Porter³

et al. 1991

257

152

“…The total magnesium excretion in our three cases of parathyroid adenoma showed no great loss of magnesium. The balances varied; in only one case (G. M.) was there a negative balance, the other two showing a greater storage of magnesium than did our normal controls on a similar intake (4).…”

mentioning

confidence: 61%

“…The observations here reported were all made on patients on the same regime and approximately the same diets as our normal controls described in Paper I of this series (4). The same methods of analysis were also used.…”

mentioning

confidence: 99%

Magnesium Metabolism in Health and Disease. Ii. The Effect of the Parathyroid Hormone

Tibbetts¹,

Aub²

1937

Self Cite

In this series of studies of the relationship between calcium, magnesium, and phosphorus exchange, the effect of the parathyroid hormone is obviously of primary interest. With the dramatic changes which occur in calcium metabolism, it might be anticipated that similar 'effects would be found in magnesium exchange, and that this might be evident in soft tissue as well as bone metabolism.Greenwald and Gross (1) found that thyroparathyroidectomy in dogs had practically no effect on magnesium excretion. A potent parathyroid extract, however, increased fecal magnesium but had no effect on the urinary excretion (2). After most of the data here recorded had been accumulated, there appeared a publication by Bulger and Gausmann (3), who stated that a loss of calcium is accompanied by a loss of magnesium in hyperparathyroidism and that retention of both accompanies postoperative recovery.Our data differ somewhat from these observations in untreated hyperparathyroidism. The total magnesium excretion in our three cases of parathyroid adenoma showed no great loss of magnesium. The balances varied; in only one case (G. M.) was there a negative balance, the other two showing a greater storage of magnesium than did our normal controls on a similar intake (4).However, when comparing the excretion in the same individual before and after parathyroidectomy we find that variations in magnesium do occur, as reported by Bulger and Gausmann (3). These variations are in the same direction though not of the same magnitude as the large changes in calcium excretion.The observations here reported were all made on patients on the same regime and approximately the same diets as our normal controls described in Paper I of this series (4). The same methods of analysis were also used. The case histories are appended.' Patient G. M. (Table I), a boy of 13, was in a serious toxic state because of an intensely overactive parathyroid adenoma. This condition was entirely relieved by operation. Very careful metabolic observations were made upon him before and promptly after the complete removal of his 11.8 gram parathyroid adenoma. A third observation on exactly the same routine was obtained three months after the operation. These studies were made with both high and low calcium diets in order to observe variations in absorption and excretion which these changes might produce, but no clear cut variation in magnesium metabolism was obvious. The slight changes in excretion were those to be anticipated from the increased magnesium ingestion necessitated by the change in diet.It is readily seen that immediately after operation there is a marked fall in urinary magnesium excretion and a less dramatic drop in the fecal magnesium. These changes, however, had partly disappeared three months after the operation, though the storage of calcium was then most dramatic. The variations of magnesium metabolism must be interpreted with due regard to changes in weight. Thus, during the pre-operative periods (I to V) and in the observation three months after his operati...

“…Prior investigations of the concentration of serum magnesium have revealed modest fluctuations unassociated with any clear-cut, consistent, clinical syndromes (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Balance studies (12)(13)(14)(15) have been hampered by the lack of low magnesium diets with the result that fluctuations in the balance have been obscured by an excessive magnesium intake and excretion. This mineral is located almost exclusively in the cells or in the skeleton, and calculations based on a standard reference (16) for the composition of the body tissues and on a generally accepted partition (17) of the anatomical compartments of the body indicate that of the 2,100 milliequivalents of magnesium present in the adult body 45 per cent are located in the skeleton.…”

mentioning

confidence: 99%

Skeletal Muscle Analyses in Health and in Certain Metabolic Disorders. I. The Method of Analysis and the Values in Normal Muscle1

Barnes¹,

Gordon²,

Cope³

1957

Tissue analyses are of special importance in regard to the meager information available today concerning the role of magnesium in disease. Prior investigations of the concentration of serum magnesium have revealed modest fluctuations unassociated with any clear-cut, consistent, clinical syndromes (1-11). Balance studies (12)(13)(14)(15) have been hampered by the lack of low magnesium diets with the result that fluctuations in the balance have been obscured by an excessive magnesium intake and excretion. This mineral is located almost exclusively in the cells or in the skeleton, and calculations based on a standard reference (16) 114-198. protoplasm, because of the accumulated information concerning its composition, and because of its availability at almost any operation.Definition of the intra-and extracellular spaces: A biochemical dissection. In the absence of an infallible technique for distinguishing between the intracellular phase and extracellular phase we have accepted the chloride space as an approximation of the extracellular space. It is well recognized that in diseased states where chloride ions may penetrate into the muscle fiber cell, the extracellular space -will be falsely enlarged. However, the chloride space still remains a most reasonable and practical means of correcting for the extracellular components to permit calculation by difference of the intracellular components. The evidence for the extracellular location of the chloride ion and for the proportionality of its total mass to the extracellular space has been recently reviewed (19).Bases of reference in expressing the concentrations of the muscle components. In tissue analyses advantages exist in expressing the results in terms of more than one reference base. Changes in the concentrations of the components in relation to one base might not appear in relating the concentrations to another due to a concomitant shift of the second base. Other considerations in the selection of a reference base are the effects of analytical variations in its determination which would cause fluctuations devoid of any biological significance and the natural variation of a reference base which should be as restricted as possible to minimize the confusion this would introduce into the interpretations. These independent characteristics may be assessed by statistical techniques outlined below.The reference base of intracellular water introduced by Hastings and Eichelberger (20) has been justified by water being the most plentiful constituent of tissues and by the success achieved in unfolding the properties of blood as a physiochemical system approximating a simple aqueous solution. More recently the use of non-collagen nitrogen (NCN), proposed by Lilienthal, Zierler, Folk, Buka, and Riley (21), as a reference base has the advantage of relating the intracellular components to a standard that is independent of any assumptions that the use of the chloride space entails in the calculation of the intracellular water. The non-collagen nitrogen, which is defined as...