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An inward rectifier K + channel at the basolateral membrane of the mouse distal convoluted tubule: similarities with Kir4‐Kir5.1 heteromeric channels
Author(s) -
Lourdel Stéphane,
Paulais Marc,
Cluzeaud Françoise,
Bens Marcelle,
Tanemoto Masayuki,
Kurachi Yoshihisa,
Vandewalle Alain,
Teulon Jacques
Publication year - 2002
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2001.012961
Subject(s) - distal convoluted tubule , chemistry , cotransporter , biophysics , epithelial polarity , conductance , membrane potential , membrane , patch clamp , biochemistry , sodium , reabsorption , biology , receptor , mathematics , organic chemistry , combinatorics
In this study, K + channels present in the basolateral membrane of the distal convoluted tubule (DCT) were investigated using patch‐clamp methods. In addition, Kir4.1, Kir4.2 and Kir5.1 inward rectifier channels were investigated using RT‐PCR and immunohistochemistry (Kir4.1). DCTs were microdissected from collagenase‐treated mouse kidneys. One type of K + channel was detected in about 50 % of cell‐attached patches from the DCT basolateral membrane; this channel was inwardly rectifying and had an inward conductance ( g in ) of ∼40 pS at an external [K + ] of 145 m m . The current‐voltage relationship was linear when inside‐out patches were exposed to a Mg 2+ ‐free medium. Mg 2+ at a concentration of 1.2 m m considerably reduced the outward conductance ( g out ), yielding a g in / g out ratio of ∼4.7. The polycation spermine (5 × 10 −7 m ) reduced the open probability ( P o ) by 50 %. Channel activity was dependent upon the intracellular pH, with acid pH decreasing, and basic pH increasing, P o . Internal ATP (2 m m ) and Ca 2+ (up to 10 −3 m ) had no effect. Channel activity declined irreversibly when the inner side of the patch was exposed to Mg 2+ . Kir4.1, Kir4.2 and Kir5.1 mRNAs were all detected in the DCT. The Kir4.1 protein co‐localised with the Na + ‐Cl − cotransporter, which is specific to the DCT, and was located on basolateral membranes. The DCT K + channel differs from other functionally identified renal K + channels with regard to its inhibition by spermine and insensitivity to internal ATP and Ca 2+ . At the current state of knowledge, the channel is similar to Kir4.1‐Kir5.1 and Kir4.2‐Kir5.1 heteromeric channels, but not to Kir4.1 or Kir4.2 homomeric channels.