[Homeostasis and magnesium--comparison with calcium].
Although Mg and Ca, bivalent cations commonly coexisting in nature and living organism, share some similar chemical properties, the role played by Mg in biological regulation and signal transduction is far less important than that by Ca. In contrast to the vast extra- and intra-cellular concentration gradient of Ca as high as 10,000, intracellular Mg is only 3 times as high as extracellular Mg. Systemic Mg metabolism including serum Mg only controlled by renal tubular reabsorption is not as precisely regulated as the Ca counterpart most precisely controlled by parathyroid hormone (PTH), 1,25 (OH)(2) vitamin D and bone. Such difference between Mg and Ca is probably based on the properties of these two kinds of atoms. Mg has a smaller ionic radius with electron arrangement making protein binding more difficult and velocity constant for water binding smaller. Signal transduction by Mg is thus destined to be much less efficient than that by Ca.
Fujita
Takuo
T
Kobe University, Katsuragi Hospital.
D002118:Calcium / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D008274:Magnesium / Q000378:metabolism / Q000502:physiology*
D008274:Magnesium; D002118:Calcium