K+
Introduction
The total body K+ content in an adult is about 2500-3000 meq. About 98% of K+ is intracellular. Concentration of K+ is about 160 meq/L intracellularly & 3.5-5.0 meq/L extracellularly. K+ is the main intracellular cation & the K+ gradient across the cell membrane provides the force behind the negative potential & electrical excitability of cells. The Na+/K+ ATPase maintains the intracellular K+ concentration.
Mechanisms regulating extracellular K+ concentration:
- renal
- most of the filtered K+ is resorbed by the proximal convoluted tubules & loop of Henle
- K+ in the urine is usually excreted by the collecting tubules under the influence of aldosterone
- factors increasing secretion of K+ in the urine
- increased urine flow rate
- increased distal tubule Na+ concentration
- increased mineralocorticoids
- aldosterone
- glucocorticoids have some mineralocorticoid activity
- increased urinary HCO3-
- urinary K+ may vary from 5-100 meq/L
- non-renal
- insulin: stimulates Na+/K+ ATPase because Na+ accompanies movement of glucose intracellularly
- beta-2 adrenergic receptor agonists
- increase activity of Na+/K+ ATPase
- aldosterone via effects on the GI tract
- acid-base balance
Dietary K+ occurs as potassium phosphate.
Generally, green leafy vegetables, fruits, & root vegetables are good dietary sources of K+. A dietary K+ intake of 120 mEq/day or more is safe for healthy people, since excess K+ is excreted in the urine. However, patients with renal insufficiency, adrenal insufficiency, the elderly, & patients on ACE inhibitors, ARBs, NSAIDs, or potassium-sparing diuretics may need to monitor K+ intake (& serum K+).[1]
More general terms
Additional terms
- dietary potassium; dietary K+
- hypokalemic (K+ depleting) agent
- potassium (K+) in body fluid
- potassium acetate
- potassium bicarbonate (Effer-K, K-lyte)
- potassium chloride (KCl, Klor Con, Kaon-Cl, Slow-K, Micro-K, Klotrix, K Tab, K Dur, Ten-K, Cen-K, Kaochlor, Kay Ciel, K Lor, Kato, Klorvess, Kaon, K Lyte Cl)
- potassium citrate (Urocit K)
- potassium hydroxide (KOH)
- potassium iodide (KI, Thyro-Block, Irostat)
- potassium phosphate (KH2PO4)
- potassium [K, kalium]
Component of
References
- ↑ 1.0 1.1 Prescriber's Letter 15(9): 2008 Potassium Content of Foods and Salt Substitutes Detail-Document#: http://prescribersletter.com/(5bhgn1a4ni4cyp2tvybwfh55)/pl/ArticleDD.aspx?li=1&st=1&cs=&s=PRL&pt=3&fpt=25&dd=240904&pb=PRL (subscription needed) http://www.prescribersletter.com
- ↑ Gumz ML, Rabinowitz L, Wingo CS An Integrated View of Potassium Homeostasis. N Engl J Med 2015; 373:60-72. July 2, 2015 <PubMed> PMID: https://www.ncbi.nlm.nih.gov/pubmed/26132942 <Internet> http://www.nejm.org/doi/full/10.1056/NEJMra1313341