Homeostasis potassium

Inward Rectifier Potassium Channels or Kir Channels are a class of potassium channels generated by tetra-meiic arrangement of one-pore/two-transmembrane helix (1P/2TM) protein subunits, often associated with additional beta-subunits. Kir channels modulate cell excitability, being involved in repolarization of action potentials (see Fig. 1), setting the resting potential (see Fig. 1) of the cell, and contributing to potassium homeostasis. 

K Channels belong to a class of membrane proteins that form highly K-selective pores in membranes. All known K Channels are composed of several (usually four) pore forming alpha subunits and auxiliary beta subunits. K Channels play an essential role in cellular excitability, being involved in repolarization of Action Potentials and setting the cell resting potential as well as contributing to potassium homeostasis. 

Potassium homeostasis refers to the maintaining and regulating of a relatively stable and mostly internal (intracellular) potassium balance (concentration), although more generally it refers to the maintenance of potassium balance in any compartment (e.g. in the blood). 

Insulin is a major regulator of potassium homeostasis and has multiple effects on sodium pump activity. Within minutes of elevated insulin secretion, pumps containing alpha-1 and 2 isoforms have increased affinity for sodium and increased turnover rate. Sustained elevations in insulin cause up-regulation of alpha-2 synthesis. In skeletal muscle, insulin may also recruit pumps stored in the cytoplasm or activate latent pumps already present in the membrane. 

Abdel-Raheem MM, Potti A, Tadros S, Koka V, Hanekom D, Fraiman G, Danielson BD. Effect of low-molecular-weight heparin on potassium homeostasis. Pathophysiol Haemost Thromb 2002 32(3) 107-10. 

Potassium homeostasis and the maintenance of serum potassium within the normal range are regulated by dietary intake. 

Sharma K, Cox M. Potassium homeostasis. In Szerlip HM, Goldfarb S, eds. Workshops in Fluid and Electrolyte Disorders. New York, Churchill Livingstone, 1993 71-96. 

Gennari FJ. Disorders of potassium homeostasis hypokalemia and hyperkalemia. Crit Care Clin 2002 18 273-288. 

Ryan MR Interrelationships of magnesium and potassium homeostasis. Miner Electrolyte Metab 1993 19 290-295. 

Gastrointestinal symptoms of metabolic acidosis include loss of appetite, nausea, and vomiting. Severe acidosis (pH <7.1) interferes with carbohydrate metabolism and insulin utilization, and results in hyperglycemia. Metabolic acidosis alters potassium homeostasis and contributes to the development of hyperkalemia. The magnimde of the effect on serum potassium depends on the type of acidosis Acidosis caused by mineral acids (e.g., hydrochloric acid) are associated with a greater change in potassium levels than acidosis caused by organic acids (e.g., lactic acidosis), in which the increase in potassium attributable to the acidosis per se is minimal. 

Wingo, C. A., and B. D. Cain. 1993. The renal H-K-ATPase. Physiological significance and role in potassium homeostasis. Annual Review of Physiology 55 323-347. 

Scandling JD, Izzo JL, Pabico RC, McKenna BA, Radke KJ, Omt DB. Potassium homeostasis during angiotensin-converting enzyme inhibition with enalapril. J Clin Pharmacol (1989) 29, 916-21. 

Schmidt A, Gruber U, Bohmig G, Koller E, Mayer G. The effect of ACE inhibitor and angiotensin II receptor antagonist therapy on serum uric acid levels and potassium homeostasis in hypertensive renal transplant recipients treated with CsA. Nephrol Dial Transplant (2001) 16, 1034-7. 

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