Colonic potassium handling.
Homeostatic control of plasma K+ is a necessary physiological function. The daily dietary K+ intake of approximately 100 mmol is excreted predominantly by the distal tubules of the kidney. About 10% of the ingested K+ is excreted via the intestine. K+ handling in both organs is specifically regulated by hormones and adapts readily to changes in dietary K+ intake, aldosterone and multiple local paracrine agonists. In chronic renal insufficiency, colonic K+ secretion is greatly enhanced and becomes an important accessory K+ excretory pathway. During severe diarrheal diseases of different causes, intestinal K+ losses caused by activated ion secretion may become life threatening. This topical review provides an update of the molecular mechanisms and the regulation of mammalian colonic K+ absorption and secretion. It is motivated by recent results, which have identified the K+ secretory ion channel in the apical membrane of distal colonic enterocytes. The directed focus therefore covers the role of the apical Ca2+ and cAMP-activated BK channel (KCa1.1) as the apparently only secretory K+ channel in the distal colon.
Department of Physiology and Biophysics, Aarhus University, Ole Worms Alle 1160, 8000 Aarhus C, Denmark.
Mads V
MV
Sorensen
Joana E
JE
Matos
Helle A
HA
Praetorius
Jens
J
Leipziger
D000818:Animals; D001692:Biological Transport; D003106:Colon / Q000502:physiology*; D007413:Intestinal Mucosa / Q000502:physiology; D011188:Potassium / Q000097:blood* / Q000378:metabolism
D011188:Potassium