[Potassium magnesium homeostasis: physiology, pathophysiology, clinical consequences of deficiency and pharmacological correction].

The metabolism of K and Mg is closely linked. Mg deficiency may arise together with and contribute to the persistence of K deficiency. Isolated disturbances of K balance do not produce secondary abnormalities in Mg homeostasis. In contrast, primary disturbances in Mg balance, particularly Mg depletion, produce secondary K depletion. This appears to result from an inability of the cell to maintain the normally high intracellular concentration of K, perhaps as a result of an increase in membrane permeability to K and / or inhibition of Na+-K+-ATPase. Cases of Mg deficiency accompanying with Mg-dependent or -independent K deficiency are not uncommon among the general population. K and Mg deficiencies are found in patients with chronic alcoholism, cardiac diseases, diabetes mellitus (type II), genetic forms of renal potassium and magnesium wasting (Gitelman's and Bartter's syndromes), severe diarrhea and vomiting, malnutrition, during therapy with some kind of drugs. Various K-Mg salts allowing simultaneously eliminating deficiency of Mg and K are described in the literature. K-Mg aspartate is most distributed among K-Mg salts. It can be used as adjuvant therapy in ischaemic heart disease (in angina pectoris and conditions after myocardial infarction), prophylaxis and adjuvant therapy of cardiac arrhythmia (e.g. prevention of toxic symptoms during therapy with digoxin). Differences in metabolism and utilisation of D- and L-amino acids probably may effect on pharmacological properties of K-Mg L- and D-aspartates, and what is more pharmacological doses of Mg and K salts may induce toxicity which differs according to the nature of the anions. In our research it was established, that L-aspartate salts are better delivery forms for cations such as Mg and K than D-aspartate salts. K-Mg L-aspartate can be more beneficial in the treatment of several forms of primary Mg and K deficiency than K-Mg DL-aspartate and K-Mg D-aspartate.

Magnesium and potassium deficiency. Its diagnosis, occurrence and treatment in diuretic therapy and its consequences for growth, protein synthesis and growth factors.

Thiazides and loop diuretics facilitate the loss of K and Mg through the kidneys leading to deficiencies that may require treatment with supplements. These losses may be overlooked, however, because serum concentrations may remain normal even when the muscle concentrations are appreciably reduced. In 76 patients who had received diuretics for 1-17 years, the mean concentrations of K, Mg and Na,K-pumps in skeletal muscle biopsies were significantly lower than in those from an age- and sexmatched control group, and muscle Mg and K concentrations were significantly correlated. The serum concentrations, however, were only below the control range in a few patients. The fact that Mg,K deficiencies may often be overlooked emphasises the need for data on the contents of skeletal muscle. A recently developed simple biopsy needle procedure permitted the detection of disorders of electrolytes during long-term diuretic treatment despite normal serum concentrations. With the same technique it was possible to detect repletion of the muscle electrolytes after a Mg supplementation period. Oral Mg supplementation could reestablish normal Mg as well as K status in patients in long-term diuretic therapy, provided that the supplementation was maintained for 6 months. Moreover, the normalization of muscle Mg and K was accompanied by a restoration of the concentration of Na,K-pumps measured as the [3H]ouabain binding site capacity in skeletal muscle. Mg and K contents were closely correlated in human muscle biopsies from patients on diuretic treatment, but also in rat muscle which had been moderately Mg depleted in vivo or in vitro. In isolated soleus muscle, which had been moderately Mg-depleted in vitro, reduction in cellular K could not be ascribed to reduced Na,K-pump mediated K-influx. The reduced K content might rather be related to increased K efflux from the muscles. In rats, insufficient dietary supplies of K, Mg and Zn were characterized by inhibition of growth and protein synthesis. These effects could not readily be related to the loss of these elements from muscle tissue, but rather should be seen as a response to a general deficiency. The most marked evidence of deficiency was seen in the serum levels, which pointed to the serum concentration as a possible mediator for the regulation of tissue growth. IGF-I is a low molecular weight peptide possessing growth promoting properties in many tissues probably as an interplay of both autocrine/paracrine and endocrine actions. In both animals and man insufficient supplies of energy and protein are accompanied by growth retardation and a decrease in serum IGF-I.(ABSTRACT TRUNCATED AT 400 WORDS)

Localization of phosphorus metabolites and sodium ions in the rat kidney.

Relative amounts of phosphorus-containing metabolites and sodium ions present in different regions of the in vivo rat kidney were obtained using a surface-coil probe and recently developed NMR rotating-frame methods. During altered physiologic states, changes in distribution of metabolites and sodium ions within the kidney were identified in one-dimensional metabolite maps. This technique may have important applications to disorders commonly found in clinical medicine.

Current approaches to management of potassium deficiency.

Current issues related to oral potassium supplementation are reviewed, with emphasis on recommendations for the appropriate use of potassium supplementation for both replacement and preventive therapy. Dietary potassium intake, potassium-sparing diuretics, and the various forms of oral potassium supplements are reviewed in terms of indications for use, advantages, and limitations. Attention is given to controversial areas, i.e., gastrointestinal tolerance of controlled-release potassium oral dosage preparations and the need for potassium supplementation in hypertensive patients treated with diuretics.

The potassium status of patients prior to open-heart surgery.

The dysrhythmia that happens after open-heart surgery has at times been attributed to potassium depletion. Therefore, in some centers, patients scheduled for open-heart surgery are routinely given potassium supplements. We have assessed the potassium status of 32 patients prior to cardiac surgery (1) by measurements of plasma, red cell, and leukocyte potassium levels and total body potassium before and after administration of potassium supplements (144 mmoles daily for 3 days) and (2) by the changes in urine potassium during the supplementation. On admission none of the patients showed evidence of a large potassium deficit, and none of them retained much of the supplemental potassium. The observations that have previously been taken as evidence of potassium depletion in such patients are discussed, and alternative explanations are suggested for all these observations.