Effects of mineralocorticoid and K+ concentration on K+ secretion and ROMK channel expression in a mouse cortical collecting duct cell line

Am J Physiol Renal Physiol. 2009 May;296(5):F966-75. doi: 10.1152/ajprenal.90475.2008. Epub 2009 Mar 18.


The cortical collecting duct (CCD) plays a key role in regulated K(+) secretion, which is mediated mainly through renal outer medullary K(+) (ROMK) channels located in the apical membrane. However, the mechanisms of the regulation of urinary K(+) excretion with regard to K(+) balance are not well known. We took advantage of a recently established mouse CCD cell line (mCCD(cl1)) to investigate the regulation of K(+) secretion by mineralocorticoid and K(+) concentration. We show that this cell line expresses ROMK mRNA and a barium-sensitive K(+) conductance in its apical membrane. As this conductance is sensitive to tertiapin-Q, with an apparent affinity of 6 nM, and to intracellular acidification, it is probably mediated by ROMK. Overnight exposure to 100 nM aldosterone did not significantly change the K(+) conductance, while it increased the amiloride-sensitive Na(+) transport. Overnight exposure to a high K(+) (7 mM) concentration produced a small but significant increase in the apical membrane barium-sensitive K(+) conductance. The mRNA levels of all ROMK isoforms measured by qRT-PCR were not changed by altering the basolateral K(+) concentration but were decreased by 15-45% upon treatment with aldosterone (0.3 or 300 nM for 1 and 3 h). The paradoxical response of ROMK expression to aldosterone could possibly work as a preventative mechanism to avoid excessive K(+) loss which would otherwise result from the increased electrogenic Na(+) transport and associated depolarization of the apical membrane in the CCD. In conclusion, mCCD(cl1) cells demonstrate a significant K(+) secretion, probably mediated by ROMK, which is not stimulated by aldosterone but increased by overnight exposure to a high K(+) concentration.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Barium / pharmacokinetics
  • Bee Venoms / pharmacology
  • Cell Line
  • Cell Polarity / physiology
  • Culture Media / pharmacology
  • Dose-Response Relationship, Drug
  • Gene Expression / drug effects
  • Gene Expression / physiology
  • Isomerism
  • Kidney Cortex / cytology
  • Kidney Cortex / physiology
  • Kidney Tubules, Collecting / cytology*
  • Kidney Tubules, Collecting / physiology*
  • Mice
  • Mineralocorticoids / metabolism*
  • Molecular Sequence Data
  • Potassium / pharmacokinetics*
  • Potassium Channels, Inwardly Rectifying / chemistry
  • Potassium Channels, Inwardly Rectifying / genetics*
  • Potassium Channels, Inwardly Rectifying / metabolism
  • RNA, Messenger / metabolism


  • Bee Venoms
  • Culture Media
  • Kcnj1 protein, mouse
  • Mineralocorticoids
  • Potassium Channels, Inwardly Rectifying
  • RNA, Messenger
  • Barium
  • tertiapin
  • Potassium