Enhanced large intestinal potassium permeability in end-stage renal disease

• Published in: The Journal of pathology Vol. 206; no. 1; pp. 46 - 51
• Main Authors: Mathialahan, T, Maclennan, KA, Sandle, LN, Verbeke, C, Sandle, GI
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.05.2005
• Subjects: Adult; Aged; Barium - pharmacology; Case-Control Studies; Cations; colon; Dialysis; end-stage renal disease; Female; Humans; Immunohistochemistry - methods; Intestinal Mucosa - secretion; Intestine, Large - metabolism; Kidney Failure, Chronic - metabolism; Kidney Failure, Chronic - physiopathology; Male; Middle Aged; Permeability; Potassium - metabolism; Potassium Channel Blockers - pharmacology; potassium channels; Potassium Channels - analysis; Potassium Channels - metabolism; potassium secretion; Rectum - secretion; Statistics, Nonparametric
• ISSN: 0022-3417; 1096-9896
• DOI: 10.1002/path.1750

The capacity of the colon for potassium (K+) secretion increases in end‐stage renal disease (ESRD), to the extent that it makes a substantial contribution to K+ homeostasis. This colonic K+ adaptive response may reflect enhanced active K+ secretion, and be associated with an increase in apical membrane K+ permeability. In this study, this hypothesis was tested in patients with normal renal function or ESRD, by evaluating the effect of barium ions (a K+ channel inhibitor) on rectal K+ secretion using a rectal dialysis technique, and the expression of high conductance (BK) K+ channel protein in colonic mucosa by immunohistochemistry. Under basal conditions, rectal K+ secretion was almost threefold greater (p < 0.02) in ESRD patients (n = 8) than in patients with normal renal function (n = 10). Intraluminal barium (5 mmol/l) decreased K+ secretion in the ESRD patients by 45% (p < 0.05), but had no effect on K+ transport in patients with normal renal function. Immunostaining using a specific antibody to the BK channel α‐subunit revealed greater (p < 0.001) levels of BK channel protein expression in surface colonocytes and crypt cells in ESRD patients (n = 9) than in patients with normal renal function (n = 9), in whom low levels of expression were mainly restricted to surface colonocytes. In conclusion, these results suggest that enhanced colonic K+ secretion in ESRD involves an increase in the apical K+ permeability of the large intestinal epithelium, which most likely reflects increased expression of apical BK channels. Copyright © 2005 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.