Dietary K+ regulates apical membrane expression of maxi-K channels in rabbit cortical collecting duct

Am J Physiol Renal Physiol. 2005 Oct;289(4):F922-32. doi: 10.1152/ajprenal.00057.2005. Epub 2005 May 24.


The cortical collecting duct (CCD) is a final site for regulation of K(+) homeostasis. CCD K(+) secretion is determined by the electrochemical gradient and apical permeability to K(+). Conducting secretory K(+) (SK/ROMK) and maxi-K channels are present in the apical membrane of the CCD, the former in principal cells and the latter in both principal and intercalated cells. Whereas SK channels mediate baseline K(+) secretion, maxi-K channels appear to participate in flow-stimulated K(+) secretion. Chronic dietary K(+) loading enhances the CCD K(+) secretory capacity due, in part, to an increase in SK channel density (Palmer et al., J Gen Physiol 104: 693-710, 1994). Long-term exposure of Ambystoma tigrinum to elevated K(+) increases renal K(+) excretion due to an increase in apical maxi-K channel density in their CDs (Stoner and Viggiano, J Membr Biol 162: 107-116, 1998). The purpose of the present study was to test whether K(+) adaptation in the mammalian CCD is associated with upregulation of maxi-K channel expression. New Zealand White rabbits were fed a low (LK), control (CK), or high (HK) K(+) diet for 10-14 days. Real-time PCR quantitation of message encoding maxi-K alpha- and beta(2-4)-subunits in single CCDs from HK animals was greater than that detected in CK and LK animals (P < 0.05); beta(1)-subunit was not detected in any CCD sample but was present in whole kidney. Indirect immunofluorescence microscopy revealed a predominantly intracellular distribution of alpha-subunits in LK kidneys. In contrast, robust apical labeling was detected primarily in alpha-intercalated cells in HK kidneys. In summary, K(+) adaptation is associated with an increase in steady-state abundance of maxi-K channel subunit-specific mRNAs and immunodetectable apical alpha-subunit, the latter observation consistent with redistribution from an intracellular pool to the plasma membrane.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Blotting, Western
  • Cations / metabolism
  • DNA Primers
  • Diet
  • Electrolytes / blood
  • Electrolytes / urine
  • Female
  • Fluorescent Antibody Technique
  • Gene Expression / drug effects
  • H(+)-K(+)-Exchanging ATPase / metabolism
  • In Vitro Techniques
  • Kidney Tubules, Collecting / drug effects
  • Kidney Tubules, Collecting / metabolism*
  • Kinetics
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
  • Large-Conductance Calcium-Activated Potassium Channels
  • Microscopy, Confocal
  • Potassium Channels, Calcium-Activated / biosynthesis*
  • Potassium Channels, Calcium-Activated / genetics
  • Potassium, Dietary / pharmacology*
  • RNA, Messenger / biosynthesis
  • Rabbits
  • Reverse Transcriptase Polymerase Chain Reaction


  • Cations
  • DNA Primers
  • Electrolytes
  • Large-Conductance Calcium-Activated Potassium Channel alpha Subunits
  • Large-Conductance Calcium-Activated Potassium Channels
  • Potassium Channels, Calcium-Activated
  • Potassium, Dietary
  • RNA, Messenger
  • H(+)-K(+)-Exchanging ATPase