True regarding Na/K pump is
|A||Pumps Na against a gradient|
|B||5 Na exchanged for 2K|
|C||Increases in intracellular Na|
|D||Hypocalcemia inhibits the pump|
Na+-K+ ATPase (pump):
- Na+-K+-ATPase catalyzes the hydrolysis of ATP to ADP and uses the energy to extrude three Na+ from the cells and take two K+ into the (ells for each mole of ATP. I.e. ↑ the ECF Na+ cone and ↑the K ICF cone or ↓the ICF Na+ cone.
- It is an Electrogenic pump, having coupling ratio 3:2 (3Na+: 2K+) Q . Since ECF conc. of Na+ is higher than ICF → so it pump Na+ outside call angaist conc. gradient and is similar way, the ICF conc. of K+ is more than ECF, hence pump K+ into the cells agaist the conc. gradient.
- Active transport of N a + and K+ is one of major energy using processes in the body on the average it accounts for about 24% of the energy utilized by cells, and in neurons it account for 70%.
- In Heart muscle, Na+-K+ ATPase indirectly affect Ca++ transport. Normally one Ca++ goes out side the cells and three Na+ go inside the cells → i.e. Antiport. If the Na+-K+ ATPase activity is inhibited by Quabain and related digitalis glycoside
i. intracellular Na+ conc. ↑es → the Na+ gradient across the cell membrane decreases → Ca++ extrusion decreases
ii. result in ↑ intracellular Ca++ conc. →↑contraction of Heart muscle → positive inotropic effect.
- Regulation of Na+-K+ ATPase activity:
Increased activity of pump
Decreased activity of pump
i. Thyroid hormone Q
ii. Aldosterone Q
iii. Insulin Q
iv. G-actin Q
i. Dopamine inhibit the pump phosphorylation in kidney, thus causes natriuresis Q
ii. Ouabain Q
- Pump activity is affected by second messengers → eg. cAMP and DAG.