cAMP Increases Apical I sK Channel Current and K + Secretion in Vestibular Dark Cells

1997 ◽  
Vol 156 (1) ◽  
pp. 25-35 ◽  
Author(s):  
H. Sunose ◽  
J. Liu ◽  
Z. Shen ◽  
D.C. Marcus
Keyword(s):  
Dark Cells ◽  
Channel Current ◽  
Sk Channel ◽  
K Secretion ◽  
Vestibular Dark Cells

Ca(2+)-activated nonselective cation channel in apical membrane of vestibular dark cells

1992 ◽  
Vol 262 (6) ◽  
pp. C1423-C1429 ◽  
Author(s):  
D. C. Marcus ◽  
S. Takeuchi ◽  
P. Wangemann
Keyword(s):  
Single Channel ◽  
Apical Membrane ◽  
Cation Channel ◽  
Nonselective Cation Channel ◽  
Channel Activity ◽  
Dark Cells ◽  
Linear Current ◽  
Current Voltage ◽  
K Secretion ◽  
Vestibular Dark Cells

Patch-clamp recordings were made on cell-attached and excised apical membrane from dark cells of the semicircular canal of the gerbil. These cells are thought to secrete K+ and absorb Na+ from the luminal fluid (endolymph). Single-channel events were identified as being equally conductive (27.6 +/- 0.4 pS; n = 48) for K+, Na+, Rb+, Li+, and Cs+ and 1.4 times more permeable to NH4+ but not permeable to Cl-, Ca2+, Ba2+, nor to N-methyl-D-glucamine. The channels displayed linear current-voltage relations that passed nearly through the origin (intercept: -2.6 +/- 0.5 mV; n = 48) when conductive monovalent cations were present on both sides of the membrane in equal concentrations. Channel activity required the presence of Ca2+ at the cytosolic face; there was no activity at less than or equal to 10(-7) M Ca2+ and full activity at greater than or equal to 10(-5) M Ca2+. Cell-attached recordings had a mean reversal voltage of -36.4 +/- 7.9 mV (n = 7), which was interpreted to reflect the intracellular potential of dark cells under the present conditions. We have identified a nonselective cation channel in the apical membrane of vestibular dark cells that might participate in K+ secretion or Na+ absorption under stimulated conditions, but the density appears to be insufficient to fully account for the transepithelial K+ flux.

Evidence for the involvement of a K+ channel in isosmotic cell shrinking in vestibular dark cells

1992 ◽  
Vol 263 (3) ◽  
pp. C616-C622 ◽  
Author(s):  
P. Wangemann ◽  
N. Shiga ◽  
C. Welch ◽  
D. C. Marcus
Keyword(s):  
Initial Rate ◽  
Basolateral Membrane ◽  
Regulatory Volume Decrease ◽  
Cell Swelling ◽  
K Channel ◽  
Control Solution ◽  
Dark Cells ◽  
Physiological Relevance ◽  
K Secretion ◽  
Vestibular Dark Cells

Cell volume changes were measured in dark cells. Isosmotic addition of 21.4 mM K+, Rb+, Cs+, or NH4+ to a control solution containing 3.6 mM K+ caused piretanide-sensitive cell swelling (initial rate for K+, 0.100 +/- 0.005 microns/s; n = 119), suggesting dependence on the Na(+)-Cl(-)-K+ cotransporter. Subsequent isosmotic removal of 21.4 mM K+ caused piretanide-insensitive cell shrinking (initial rate, -0.104 +/- 0.005 microns/s; n = 119), which was inhibited by barium, lidocaine, quinidine, quinine, verapamil, and 4-aminopyridine but not tetraethylammonium (TEA) or glibenclamide, suggesting the involvement of K+ channel(s). Barium, lidocaine, quinine, quinidine, and 4-aminopyridine caused cell swelling in control solution (initial rate for barium, 0.011 +/- 0.004 microns/s; n = 6), suggesting that the K+ channel is also involved in efflux under control conditions. Cell shrinking was slowed by 21.4 mM extracellular K+, Rb+, or Cs+ but unaffected by Na+, Li+, TEA+, or NH4+ (all in the presence of piretanide and compared with N-methyl-D-glucamine), supporting the notion that the efflux mechanism is permeable to and/or inhibited by K+, Rb+, and Cs+. Cell shrinking was slowed by the presumed replacement of intracellular K+ by Cs+ but not by Rb+. Circumstantial evidence suggests that this putative K+ channel is present in the basolateral membrane. The physiological relevance of such a K+ channel might encompass regulatory volume decrease during K+ secretion.

K+-induced stimulation of K+ secretion involves activation of the IsK channel in vestibular dark cells

1996 ◽  
Vol 100 (1-2) ◽  
pp. 201-210 ◽  
Author(s):  
Philine Wangemann ◽  
Zhijun Shen ◽  
Jianzhong Liu
Keyword(s):  
Dark Cells ◽  
K Secretion ◽  
Vestibular Dark Cells ◽  
Stimulation Of

Vestibular dark cells contain the exchanger NHE-1 in the basolateral membrane

1996 ◽  
Vol 94 (1-2) ◽  
pp. 94-106 ◽  
Author(s):  
Philine Wangemann ◽  
Jianzhong Liu ◽  
Nobuyuki Shiga
Keyword(s):  
Basolateral Membrane ◽  
Dark Cells ◽  
Vestibular Dark Cells
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