Regulation of intracellular magnesium by Mg2+ efflux.
Chicken erythrocytes were loaded with Mg2+ by incubation with the cation ionophore A 23187 in the presence of Mg2+. After removing A 23187 by intensive washing with serum albumin and reincubating the Mg2+-loaded cells, Mg2+ was transported out of the cells until the original Mg2+ content was achieved. The net Mg2+ efflux followed Michaelis-Menten-kinetics and was independent of extracellular and intracellular Ca2+ and calmodulin. The net Mg2+ efflux was not affected by adrenalin, isoproterenol, p-chloromercuribenzenesulfonate, ouabain and tetrodotoxin, but was inhibited by dicyclohexylcarbodiimide, KCN, iodoacetate, high extracellular concentrations of Mg2+, Mn2+ and when extracellular Na+ was substituted by choline or K+. The efflux of 1 Mg2+ was coupled with the uptake of 2 Na+. It is concluded that there exists an additional gating process at the inner cell surface becoming active only at increased concentrations of intracellular free Mg2+ regulating the exit of Mg2+ by the efflux system.
D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D000001:Calcimycin / Q000494:pharmacology; D002645:Chickens; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D004912:Erythrocytes / Q000187:drug effects / Q000378:metabolism*; D007461:Iodoacetates / Q000494:pharmacology; D019807:Iodoacetic Acid; D007700:Kinetics; D008274:Magnesium / Q000097:blood* / Q000494:pharmacology; D011190:Potassium Cyanide / Q000494:pharmacology
D007461:Iodoacetates; D000001:Calcimycin; D004024:Dicyclohexylcarbodiimide; D008274:Magnesium; D011190:Potassium Cyanide; D019807:Iodoacetic Acid