Intra-/extracellular shifts of potassium after the administration of Mg in patients with cardiovascular diseases.

Body potassium status is often dosed on serum potassium determinations. However, this parameter is not an adequate guide to the body potassium status, unless several factors are taken into consideration, e.g. acid-base balance and serum creatinine level. Muscle magnesium content is another factor, probably operative through its activation of Na-K-ATPase, which produces the energy necessary for the active transport of potassium into the cell. Magnesium has a membrane-stabilizing effect as well, diminishing the outward movement of potassium from the cell. In case of magnesium deficiency, potassium cannot be transported into the cell in sufficient amounts and the result is an imbalance between the intra- and the extracellular potassium concentration, which in turn may lead to cardiac dysrhythmias.