Kir4.1/Kir5.1 channel forms the major K+ channel in the basolateral membrane of mouse renal collecting duct principal cells

Am J Physiol Renal Physiol. 2008 Jun;294(6):F1398-407. doi: 10.1152/ajprenal.00288.2007. Epub 2008 Mar 26.

Abstract

K(+) channels in the basolateral membrane of mouse cortical collecting duct (CCD) principal cells were identified with patch-clamp technique, real-time PCR, and immunohistochemistry. In cell-attached membrane patches, three K(+) channels with conductances of approximately 75, 40, and 20 pS were observed, but the K(+) channel with the intermediate conductance (40 pS) predominated. In inside-out membrane patches exposed to an Mg(2+)-free medium, the current-voltage relationship of the intermediate-conductance channel was linear with a conductance of 38 pS. Addition of 1.3 mM internal Mg(2+) had no influence on the inward conductance (G(in) = 35 pS) but reduced outward conductance (G(out)) to 13 pS, yielding a G(in)/G(out) of 3.2. The polycation spermine (6 x 10(-7) M) reduced its activity on inside-out membrane patches by 50% at a clamp potential of 60 mV. Channel activity was also dependent on intracellular pH (pH(i)): a sigmoid relationship between pH(i) and channel normalized current (NP(o)) was observed with a pK of 7.24 and a Hill coefficient of 1.7. By real-time PCR on CCD extracts, inwardly rectifying K(+) (Kir)4.1 and Kir5.1, but not Kir4.2, mRNAs were detected. Kir4.1 and Kir5.1 proteins cellularly colocalized with aquaporin 2 (AQP2), a specific marker of CCD principal cells, while AQP2-negative cells (i.e., intercalated cells) showed no staining. Dietary K(+) had no influence on the properties of the intermediate-conductance channel, but a Na(+)-depleted diet increased its open probability by approximately 25%. We conclude that the Kir4.1/Kir5.1 channel is a major component of the K(+) conductance in the basolateral membrane of mouse CCD principal cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Polarity / physiology*
  • Cloning, Molecular
  • Immunohistochemistry
  • In Vitro Techniques
  • Kidney Cortex / physiology
  • Kidney Tubules, Collecting / cytology*
  • Kidney Tubules, Collecting / physiology*
  • Male
  • Mice
  • Mice, Inbred Strains
  • Models, Biological
  • Patch-Clamp Techniques
  • Potassium Channels, Inwardly Rectifying / genetics
  • Potassium Channels, Inwardly Rectifying / physiology*
  • Potassium, Dietary / pharmacokinetics
  • RNA, Messenger / metabolism
  • Sodium, Dietary / pharmacokinetics

Substances

  • Kcnj10 (channel)
  • Kir4.2 channel
  • Kir5.1 channel
  • Potassium Channels, Inwardly Rectifying
  • Potassium, Dietary
  • RNA, Messenger
  • Sodium, Dietary