Sodium-potassium adenosine triphosphate

O Brien WJ, Lingrel JB, Wallick ET (1994) Ouabain binding kinetics of the rat alpha two and alpha 3 isoforms of the sodium-potassium adenosine triphosphate. Arch Biochem Biophys 310 32-39... 

Post, R.L., Hegyvary, C., Kume, S. (1972). Activation by adenosine triphosphate in the phosphorylation kinetics of sodium and potassium ion transport adenosine triphosphatase. J. Biol. Chem. 247, 6530-6540. 

ATP adenosine triphosphate NaMC-AT- Pase sodium and potassium ions stimulated adenoisine triphos-... 

Pumps are proteins that can transport ions against electrochemical potential gradients using adenosine-5-triphosphate (ATP) as an energy source. Sodium-potassium pumps maintain intracellular sodium and potassium concentrations in animal cells and also control salt and water absorption by the epithelial cells in the intestine and kidney. The sodium-potassium pump transports three sodium ions out of the cell and two potassium ions into the cell at the cost of one molecule of ATP. The 3 2 coupling ratio results in net loss of sodium ions into the cell down an electrochemical gradient and maintains cell volume. Currently, considerable research is attempting to elucidate the structures of the various isoforms and subunits of sodium potassium pumps. 

The primary mechanism of terbutaline is the stimulation of adenylcyclase, which catalyzes cyclic adenosine monophosphate (AMP) from adenosine triphosphate (ATP). In the liver, buildup of cyclic AMP stimulates glycogenolysis and an increase in serum glucose. In skeletal muscle, this process results in increased lactate production. Direct stimulus of sodium/potassium AT-Pase in skeletal muscle produces a shift of potassium from the extracellular space to the intracellular space. Relaxation of smooth muscle produces a dilation of the vasculamre supplying skeletal muscle, which results in a drop in diastolic and mean arterial pressure (MAP). Tachycardia occurs as a reflex to the drop in MAP or as a result of Pi stimulus. )Si-Adrenergic receptors in the locus ceruleus also regulate norepinephrine-induced inhibitory effects, resulting in agitation, restlessness, and tremor. 

Muscles contract when potassium moves out the cell and is replaced by sodium (see 10.16 Sodium). Sodium is outside the cell. Potassium and sodium reverse positions to repolarize the muscle. The sodium-potassium pump located in cell membranes maintains the potassium and sodium balance. The sodium-potassium pump uses adenosine triphosphate (ATP) to pump potassium into the cell and sodium out of the cell. 

Sen, A. K., Post, R. L. Stoichiometry and locahzation of adenosine triphosphate-dependent sodium and potassium transport in the erythrocyte. J. Biol. Chem. 1964,239, 345-352. 

Triphosphoric acid adenosine ester. See Adenosine triphosphate Triphosphoric acid pentapotassium salt. See Potassium tripolyphosphate Triphosphoric acid pentasodium salt Triphosphoric acid sodium salt. See Pentasodium triphosphate Tripiperazine dicitrate. See Piperazine citrate... 

This enzyme activity has been observed in myosin and actomyosin, mitochondria, microsomes, and cell membranes. In some cases magnesium ions function as an activator, in others calcium ions, and in still others, both calcium and magnesium are requited. Another form of adenosine-triphosphatase is stimulated by sodium and potassium ions and is inhibited by ouabain. Some forms of the enzyme can hydrolyse inosine triphosphate and other nucleoside-5 -triphosphates. The substrate specificity may depend upon the activating divalent cation and on the presence of monovalent cations. These enzymes are probably important components of a system responsible for facilitating cation transfer in membranes. They should not be confused with adenosine triphosphate pyrophosphatase E.C. 3.6.1.8. 

Sodium also plays an important role in nerve impulse generation and transmission. As a part of the sodium-potassium pump, the difference between the potassium and sodium concentrations is maintained through active transport across the cell membrane as needed with the help of adenosine triphosphate (ATP) as an energy source. The flow of sodium and potassium across the cell membrane of electrically charged cells results in depolarization. Thus sodium is important for nerve and muscle function. As such, sodium imbalances can affect cardiac and respiratory muscle function as well as mobility. 

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