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This Article Full Text Full Text (PDF) All Versions of this Article: 294/6/F1398    most recent 00288.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Lachheb, S. Articles by Paulais, M. PubMed PubMed Citation Articles by Lachheb, S. Articles by Paulais, M.

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

¹Université Pierre et Marie Curie-Paris 6 and ²Centre National de la Recherche Scientifique, UMR7134, ³Institut National de la Santé et de la Recherche Médicale U773, Centre de Recherche Biomédicale Bichat-Beaujon (CRB3), and ⁴Université Paris 7-Denis Diderot, Paris, France; and ⁵Division of Cellular and Molecular Pharmacology, Department of Pharmacology, Graduate School of Medicine, Osaka University, Osaka, Japan

Submitted 25 June 2007 ; accepted in final form 17 March 2008

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 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 Mg²⁺-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 Mg²⁺ 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 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.

kidney; patch clamp