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

Abstract

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...

Magnesium Metabolism in Primary Hyperparathyroidism

“…Its more prolonged administration has apparently caused an increased urinary excretion of magnesium in man (Bulger & Gaussman, 1933;Tibbetts & Aub, 1937b;Gill et al, 1967). While the latter effect would tend to deplete body stores of magnesium, it appears from the present study and others (Heaton & Pyrah, 1963;Bassett & Van Alstine, 1935) that the urinary losses are usually offset by intestinal absorption. In view of this, and the tendency for the action of parathyroid hormone on bone and kidney to sustain or elevate the serum magnesium, it is necessary to seek alternative explanations for the exceptional case with hypomagnesaemia.…”

“…Because of the duration of these metabolic studies, deviations of magnesium balance from equilibrium were considered probably significant when they exceeded k 5% of the magnesium intake. When the external nitrogen balance was positive, it has been assumed that this entailed an obligatory retention of 0.63 mEq (7.6 mg) of magnesium in soft tissue for each lg of nitrogen retained (Baldwin, Robinson, Zierler & Lilienthal, 1952;Barnes, Gordon & Cope, 1957b).…”

Variability in the water, sodium, potassium, and chloride content of human skeletal muscle

“…Analysis of published data of other investigators (Talso, Spafford, and Blaw, 1953a, b;Barnes, Gordon, and Cope, 1957;Litchfield and Gaddie, 1958) shows a similar lack of effect of reference bases on the variability of sodium, potassium, and chloride.…”

Values for tissue magnesium as a guide in detecting magnesium deficiency

“…Their method was adopted here. It is interesting that the mean value, calculated from the data of other workers (Wilson 1955;Barnes, Gordon, and Cope 1957), who analysed undried muscle, was 16-7 m-equiv Mg and 792 g H2O per kg of fresh muscle. This works out to be about 80 mequiv/kg dry, fat-free solids, a figure reasonably close to, though somewhat higher than, our value and those of Maclntyre et al (1961).…”