Biomaterial Database

The magnesium dependence of sodium-pump-mediated sodium-potassium and sodium-sodium exchange in intact human red cells. 1981

P W Flatman, and V L Lew

1. The magnesium content of human red blood cells was controlled by varying the magnesium concentration in the medium in the presence of the ionophore A23187. The new magnesium levels attained were very stable, which allowed the magnesium dependence of the sodium pump to be investigated.2. The effects of magnesium were shown to occur at the inner surface of the red cell membrane for the range of magnesium concentrations tested (10(-7) to 6 x 10(-3)m).3. At intracellular ionized magnesium concentrations below 0.8 mm the activation of ouabain-sensitive sodium-potassium exchange by internal ionized magnesium could be resolved into two or three components: (a) a small component, about 5% of the maximum flux, which is apparently independent of the ionized magnesium concentration below 2 mum, (b) a saturating component with a K((1/2)) of between 30 and 45 mum, and possibly (c) a component which increases linearly with ionized magnesium concentration and which only becomes apparent at concentrations above 0.1 mm.4. At intracellular ionized magnesium concentrations below 0.8 mm, activation of ouabain-sensitive sodium-sodium exchange by internal ionized magnesium could be resolved into two components: (a) a small component, about 6% of the maximal flux, which is apparently independent of the ionized magnesium concentration below 2 mum, and (b) a saturating component with a K((1/2)) of about 9 mum. At ionized magnesium concentrations between about 0.2 and 0.8 mm the rate of sodium-sodium exchange remained constant at the maximal level.5. The intracellular concentration of ATP decreased and the ADP concentration increased as the magnesium content of the cells was reduced from the normal level. A small increase in ATP and a small decrease in ADP was seen when the magnesium content was increased above the normal level. The variation in the ATP: ADP ratio from 2.5 at very low magnesium levels to about 6 at normal magnesium levels can account, at least in part, for the different K((1/2)) values of sodium-potassium and sodium-sodium exchange.6. When the concentration of ionized magnesium was increased above about 0.8 mm both sodium-potassium and sodium-sodium exchange were inhibited. Sodium-sodium exchange was more strongly inhibited than sodium-potassium exchange.7. The possible sites of action of magnesium in the sodium pump cycle are discussed.

UI	MeSH Term	Description	Entries
D008274	Magnesium	A metallic element that has the atomic symbol Mg, atomic number 12, and atomic weight 24.31. It is important for the activity of many enzymes, especially those involved in OXIDATIVE PHOSPHORYLATION.
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D011188	Potassium	An element in the alkali group of metals with an atomic symbol K, atomic number 19, and atomic weight 39.10. It is the chief cation in the intracellular fluid of muscle and other cells. Potassium ion is a strong electrolyte that plays a significant role in the regulation of fluid volume and maintenance of the WATER-ELECTROLYTE BALANCE.
D004912	Erythrocytes	Red blood cells. Mature erythrocytes are non-nucleated, biconcave disks containing HEMOGLOBIN whose function is to transport OXYGEN.	Blood Cells, Red,Blood Corpuscles, Red,Red Blood Cells,Red Blood Corpuscles,Blood Cell, Red,Blood Corpuscle, Red,Erythrocyte,Red Blood Cell,Red Blood Corpuscle
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000001	Calcimycin	An ionophorous, polyether antibiotic from Streptomyces chartreusensis. It binds and transports CALCIUM and other divalent cations across membranes and uncouples oxidative phosphorylation while inhibiting ATPase of rat liver mitochondria. The substance is used mostly as a biochemical tool to study the role of divalent cations in various biological systems.	4-Benzoxazolecarboxylic acid, 5-(methylamino)-2-((3,9,11-trimethyl-8-(1-methyl-2-oxo-2-(1H-pyrrol-2-yl)ethyl)-1,7-dioxaspiro(5.5)undec-2-yl)methyl)-, (6S-(6alpha(2S,3S),8beta(R*),9beta,11alpha))-,A-23187,A23187,Antibiotic A23187,A 23187,A23187, Antibiotic
D000244	Adenosine Diphosphate	Adenosine 5'-(trihydrogen diphosphate). An adenine nucleotide containing two phosphate groups esterified to the sugar moiety at the 5'-position.	ADP,Adenosine Pyrophosphate,Magnesium ADP,MgADP,Adenosine 5'-Pyrophosphate,5'-Pyrophosphate, Adenosine,ADP, Magnesium,Adenosine 5' Pyrophosphate,Diphosphate, Adenosine,Pyrophosphate, Adenosine
D000255	Adenosine Triphosphate	An adenine nucleotide containing three phosphate groups esterified to the sugar moiety. In addition to its crucial roles in metabolism adenosine triphosphate is a neurotransmitter.	ATP,Adenosine Triphosphate, Calcium Salt,Adenosine Triphosphate, Chromium Salt,Adenosine Triphosphate, Magnesium Salt,Adenosine Triphosphate, Manganese Salt,Adenylpyrophosphate,CaATP,CrATP,Manganese Adenosine Triphosphate,MgATP,MnATP,ATP-MgCl2,Adenosine Triphosphate, Chromium Ammonium Salt,Adenosine Triphosphate, Magnesium Chloride,Atriphos,Chromium Adenosine Triphosphate,Cr(H2O)4 ATP,Magnesium Adenosine Triphosphate,Striadyne,ATP MgCl2
D001693	Biological Transport, Active	The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy.	Active Transport,Uphill Transport,Active Biological Transport,Biologic Transport, Active,Transport, Active Biological,Active Biologic Transport,Transport, Active,Transport, Active Biologic,Transport, Uphill
D012964	Sodium	A member of the alkali group of metals. It has the atomic symbol Na, atomic number 11, and atomic weight 23.	Sodium Ion Level,Sodium-23,Ion Level, Sodium,Level, Sodium Ion,Sodium 23