Functional compartmentation of intracellular magnesium.

Due to the distribution of Mg2+-binding ligands, such as DNA, RNA, or Mg2+-binding proteins, e.g. within the intermembranous space of mitochondria, intracellular magnesium is compartmentalized. Furthermore, cytosolic free Mg2+ is enriched at charged surfaces. Thus, the exact concentration of free intracellular Mg2+ can only be ascertained for a small volume element. Compartmentation of intracellular Mg2+ can also be determined by flux measurements with 28Mg2+. In different cell types, cellular Mg2+ is exchanged with different velocities, and, in some cell types, rapidly and slowly or non-exchangeable compartments are detectable. Cells can be Mg2+-depleted gradually by incubation with A23187 and EDTA. In cells which are Mg2+-depleted gradually, the Mg2+-dependent metabolic functions are inhibited in the following sequence: glycolysis, RNA, DNA synthesis, respiration, protein synthesis, protein synthesis appears to be the most sensitive function affected.