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The 70 pS Inward Rectifying K Channel Is Identified as Renal Outer Medullary K Channels (ROMK) on Rough, but not Smooth, Thick Ascending Limb Cells (TAL)
Author(s) -
Li Huaqing,
wang Bangchen,
WangFrance Jun,
Bayles Cayla,
Verlander Jill W.,
Sansom Steven C
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.857.15
Subject(s) - chemistry , biophysics , patch clamp , potassium channel , anatomy , nephron , biology , biochemistry , receptor , renal function
Previous studies revealed that ROMK was represented by two inward rectifying K‐selective channels (K ir ) in the TAL, with single channel conductances of approximately 30 pS and 70 pS (inward currents). However, the mouse TAL contains two types of cells; rough TAL (R‐TAL), with abundant apical microvilli and smooth TAL (S‐TAL), which are absent of microvilli. We performed patch clamping, immunohistochemistry, and electron microscopy with immunogold in attempt to determine whether the 30 pS and/or 70 pS channels were associated with R‐TAL or S‐TAL. Cell‐attached patches with 140 mM KCl in the pipette, applied to the split‐open TAL from WT or ROMK knock‐out mice (KO) (one tubule/mouse and 4 to 9 patches per tubule), revealed the 30 pS K ir (31.1 ± 1.2 pS) with an open probability of 0.60 ± 0.09 (at −Vp = −40 mV) and a density of 20 channels out of 73 patches. The 70 pS K ir (74.0 ± 3.4 pS) was observed with P o of 0.35 ± 0.13, and with a density of 12 channels out of 73 patches. We found no patches that contained both channels despite a mathematical probability that 5 patches would contain both the 30 pS and 70 pS channels. We found no 70 pS channels in 42 patches of TAL from ROMK−/−. However, 17 channels were identified as the 30 pS K ir (34.2 ± 1.0) with a P o of 0.56 ± 0.06 (−Vp = −40 mV). Co‐immunohistochemical staining with anti‐ROMK (from Dr. Paul Welling) and anti‐Tamm‐Horsfall protein (TAL marker) revealed ROMK on the luminal membrane of only 40 to 60% of the TAL cells. Using immunogold‐labeled anti‐ROMK and transmission electron microscopy, we found that ROMK was associated with the R‐TAL but not S‐TAL. We conclude that the 70 pS, but not the 30 pS K ir , represents ROMK and the 70 pS K ir is predominantly localized on R‐TAL Support or Funding Information This project is supported by the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) grants R01‐DK‐092474 and R01‐DK‐071014