Kir4.1/Kir5.1 channel forms the major K+ channel in the basolateral membrane of mouse renal collecting duct principal cells.
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.
Lachheb
Sahran
S
Université Pierre et Marie Curie, 75720 Paris Cedex 06, France.
Cluzeaud
Françoise
F
Bens
Marcelle
M
Genete
Mathieu
M
Hibino
Hiroshi
H
Lourdel
Stéphane
S
Kurachi
Yoshihisa
Y
Vandewalle
Alain
A
Teulon
Jacques
J
Paulais
Marc
M
D000818:Animals; D016764:Cell Polarity / Q000502:physiology*; D003001:Cloning, Molecular; D007150:Immunohistochemistry; D066298:In Vitro Techniques; D007672:Kidney Cortex / Q000502:physiology; D007685:Kidney Tubules, Collecting / Q000166:cytology* / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D008954:Models, Biological; D018408:Patch-Clamp Techniques; D024661:Potassium Channels, Inwardly Rectifying / Q000235:genetics / Q000502:physiology*; D017419:Potassium, Dietary / Q000493:pharmacokinetics; D012333:RNA, Messenger / Q000378:metabolism; D012982:Sodium, Dietary / Q000493:pharmacokinetics; D000097062:Kir5.1 Channel; D000098854:Kcnj10 Channel
D024661:Potassium Channels, Inwardly Rectifying; D017419:Potassium, Dietary; D012333:RNA, Messenger; D012982:Sodium, Dietary; D000097062:Kir5.1 Channel; D000098854:Kcnj10 Channel; C489469:Kir4.2 channel