Inhibitors of the Cl - /HCO 3 - exchanger activate an anion channel with similar features in the epithelial cells of rabbit gallbladder: patch-clamp analysis

2001 ◽  
Vol 441 (4) ◽  
pp. 467-473 ◽  
Author(s):  
G. Meyer ◽  
C. Porta ◽  
M. Garavaglia ◽  
D. Cremaschi
Keyword(s):  
Epithelial Cells ◽  
Patch Clamp ◽  
Anion Channel ◽  
Rabbit Gallbladder

Different sodium chloride cotransport systems in the apical membrane of rabbit gallbladder epithelial cells

1983 ◽  
Vol 73 (3) ◽  
pp. 227-235 ◽  
Author(s):  
Dario Cremaschi ◽  
Giuliano Meyer ◽  
Sandra Bermano ◽  
Maurizia Marcati
Keyword(s):  
Sodium Chloride ◽  
Epithelial Cells ◽  
Apical Membrane ◽  
Rabbit Gallbladder ◽  
Cotransport Systems

Ionic channels in corneal endothelium

1996 ◽  
Vol 270 (4) ◽  
pp. C975-C989 ◽  
Author(s):  
J. L. Rae ◽  
M. A. Watsky
Keyword(s):  
Patch Clamp ◽  
Corneal Endothelium ◽  
Single Channel ◽  
Cell Voltage ◽  
Anion Channel ◽  
Ionic Channels ◽  
K Channel ◽  
Na Channel ◽  
Channel Blockers ◽  
K Currents

Single-channel patch-clamp techniques as well as standard and perforated-patch whole cell voltage-clamp techniques have been applied to the study of ionic channels in the corneal endothelium of several species. These studies have revealed two major K+ currents. One is due to an anion- and temperature-stimulated channel that is blocked by Cs+ but not by most other K+ channel blockers, and the other is similar to the family of A-currents found in excitable cells. The A-current is transient after a depolarizing voltage step and is blocked by both 4-aminopyridine and quinidine. These two currents are probably responsible for setting the -50 to -60 mV resting voltage reported for these cells. A Ca(2+)-activated ATP-inhibited nonselective cation channel and a tetrodotoxin-blocked Na+ channel are possible Na+ inflow pathways, but, given their gating properties, it is not certain that either channel works under physiological conditions. A large-conductance anion channel has also been identified by single-channel patch-clamp techniques. Single corneal endothelial cells have input resistances of 5-10 G omega and have steady-state K+ currents that are approximately 10 pA at the resting voltage. Pairs or monolayers of cells are electrically coupled and dye coupled through gap junctions.

Apparent intermediate K conductance channel hyposmotic activation in human lens epithelial cells

2008 ◽  
Vol 294 (3) ◽  
pp. C820-C832 ◽  
Author(s):  
Peter K. Lauf ◽  
Sandeep Misri ◽  
Ameet A. Chimote ◽  
Norma C. Adragna
Keyword(s):  
Epithelial Cells ◽  
Regulatory Volume Decrease ◽  
Anion Channel ◽  
Human Lens ◽  
Lens Epithelial Cells ◽  
K Channel ◽  
Channel Blockers ◽  
Rt Pcr ◽  
Cell Water ◽  
Human Lens Epithelial Cells

This study explores the nature of K fluxes in human lens epithelial cells (LECs) in hyposmotic solutions. Total ion fluxes, Na-K pump, Cl-dependent Na-K-2Cl (NKCC), K-Cl (KCC) cotransport, and K channels were determined by 85Rb uptake and cell K (Kc) by atomic absorption spectrophotometry, and cell water gravimetrically after exposure to ouabain ± bumetanide (Na-K pump and NKCC inhibitors), and ion channel inhibitors in varying osmolalities with Na, K, or methyl-d-glucamine and Cl, sulfamate, or nitrate. Reverse transcriptase polymerase chain reaction (RT-PCR), Western blot analyses, and immunochemistry were also performed. In isosmotic (300 mosM) media ∼90% of the total Rb influx occurred through the Na-K pump and NKCC and ∼10% through KCC and a residual leak. Hyposmotic media (150 mosM) decreased Kc by a 16-fold higher K permeability and cell water, but failed to inactivate NKCC and activate KCC. Sucrose replacement or extracellular K to >57 mM, but not Rb or Cs, in hyposmotic media prevented Kc and water loss. Rb influx equaled Kc loss, both blocked by clotrimazole (IC50 ∼25 μM) and partially by 1-[(2-chlorophenyl) diphenylmethyl]-1H-pyrazole (TRAM-34) inhibitors of the IK channel KCa3.1 but not by other K channel or connexin hemichannel blockers. Of several anion channel blockers (dihydro-indenyl)oxy]alkanoic acid (DIOA), 4-2(butyl-6,7-dichloro-2-cyclopentylindan-1-on-5-yl)oxybutyric acid (DCPIB), and phloretin totally or partially inhibited Kc loss and Rb influx, respectively. RT-PCR and immunochemistry confirmed the presence of KCa3.1 channels, aside of the KCC1, KCC2, KCC3 and KCC4 isoforms. Apparently, IK channels, possibly in parallel with volume-sensitive outwardly rectifying Cl channels, effect regulatory volume decrease in LECs.

scholarly journals Prolactin stimulates sodium and chloride ion channels in A6 renal epithelial cells

2015 ◽  
Vol 308 (7) ◽  
pp. F697-F705 ◽  
Author(s):  
Megan M. Greenlee ◽  
Jeremiah D. Mitzelfelt ◽  
Billie Jeanne Duke ◽  
Otor Al-Khalili ◽  
Hui-Fang Bao ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Chloride Transport ◽  
Anion Channel ◽  
Chloride Ion ◽  
Peptide Hormone ◽  
Open Probability ◽  
Renal Epithelial Cells ◽  
Electrophysiological Properties ◽  
A6 Cells ◽  
Pka Pathway

Many hormonal pathways contribute to the regulation of renal epithelial sodium channel (ENaC) function, a key process for maintaining blood volume and controlling blood pressure. In the present study, we examined whether the peptide hormone prolactin (PRL) regulates ENaC function in renal epithelial cells (A6). Basolateral application of several different concentrations of PRL dramatically stimulated the transepithelial current in A6 cells, increasing both amiloride-sensitive (ENaC) and amiloride-insensitive currents. Using cell-attached patch clamp, we determined that PRL increased both the number ( N) and open probability ( Po) of ENaC present in the apical membrane. Inhibition of PKA with H-89 abolished the effect of PRL on amiloride-sensitive and insensitive transepithelial currents and eliminated the increase in ENaC NPo with PRL exposure. PRL also increased cAMP in A6 cells, consistent with signaling through the cAMP-dependent PKA pathway. We also identified that PRL induced activity of a 2-pS anion channel with outward rectification, electrophysiological properties consistent with ClC4 or ClC5. RT-PCR only detected ClC4, but not ClC5 transcripts. Here, we show for the first time that PRL activates sodium and chloride transport in renal epithelial cells via ENaC and ClC4.

Mechanism of sodium hyperabsorption in cultured cystic fibrosis nasal epithelium: a patch-clamp study

1994 ◽  
Vol 266 (4) ◽  
pp. C1061-C1068 ◽  
Author(s):  
T. C. Chinet ◽  
J. M. Fullton ◽  
J. R. Yankaskas ◽  
R. C. Boucher ◽  
M. J. Stutts
Keyword(s):  
Cystic Fibrosis ◽  
Epithelial Cells ◽  
Patch Clamp ◽  
Single Channel ◽  
Apical Membrane ◽  
Channel Conductance ◽  
Single Channel Conductance ◽  
Open Probability ◽  
Nasal Epithelial Cells ◽  
Na Permeability

Transepithelial Na+ absorption is increased two to three times in cystic fibrosis (CF) compared with normal (NL) airway epithelia. This increase has been associated with a higher Na+ permeability of the apical membrane of airway epithelial cells. Because Na+ absorption is electrogenic and abolished by amiloride, Na+ channels are thought to dominate the apical membrane Na+ permeability. Three Na+ channel-related mechanisms may explain the increase in apical Na+ permeability in CF cells: increased number of channels, increased single-channel conductance, and increased single-channel open probability. We compared the properties of Na(+)-permeable channels in the apical membrane of confluent preparations of human NL and CF nasal epithelial cells cultured on permeable supports. Na(+)-permeable channels were studied using the patch-clamp technique in the excised inside-out and cell-attached configurations. The same types of Na(+)-permeable channels were recorded in CF and NL cells. In excised patches, nonselective (Na+/K+) cation channels were recorded, and no differences between CF and NL were found in the properties, incidence, single-channel conductance, and single-channel open probability. In cell-attached patches, channels with a higher Na+ vs. K+ selectivity dominated. There was no difference between CF and NL cells in the incidence (18.8 vs. 21.4%, respectively) and conductance (17.2 +/- 2.8 vs. 21.4 +/- 1.5 pS, respectively) of Na(+)-permeable channels. However, the open probability was higher in CF cells compared with NL cells (30.0 +/- 3.4%, n = 6, vs. 15.0 +/- 3.9%, n = 13; P < 0.05). We conclude that, in CF nasal epithelial cells, the increase in Na+ permeability of the apical membrane results from an increase in the open probability of Na(+)-permeable channels in the apical membrane.

Characterization of cyclic AMP-regulated chloride conductance in the pigmented rabbit conjunctival epithelial cells

2002 ◽  
Vol 80 (6) ◽  
pp. 533-540 ◽  
Author(s):  
Michael H.I Shiue ◽  
Hovhannes J Gukasyan ◽  
Kwang-Jin Kim ◽  
Donald D.F Loo ◽  
Vincent H.L Lee
Keyword(s):  
Epithelial Cells ◽  
Cyclic Amp ◽  
Patch Clamp ◽  
Reversal Potential ◽  
Partial Substitution ◽  
Bathing Solution ◽  
Transmembrane Conductance Regulator ◽  
Whole Cell ◽  
C Terminus ◽  
Conjunctival Epithelial Cells

We have previously reported that the pigmented rabbit conjunctiva is a Cl– secreting tissue, subject to cAMP, Ca2+, and PKC modulation. The present study was conducted to characterize, at the cellular and molecular levels, cAMP-regulated Cl– channels in rabbit conjunctival epithelial cells. cAMP-inducible Cl– channel properties were evaluated by monitoring the whole-cell currents using patch clamp techniques. Results showed that 10 μM forskolin significantly stimulated a glibenclamide-inhibitable whole-cell conductance by approximately five-fold. Furthermore, reduction of the Cl– concentration in the bathing solution through partial substitution of NaCl with Na-isethionate resulted in a rightward shift of the reversal potential for both baseline and forskolin-stimulated whole-cell currents from 0 to values close to the theoretical Cl– reversal potential predicted by the Nernst equation. Western blot analysis with a monoclonal antibody recognizing the epitope in the C-terminus of the cystic fibrosis transmembrane conductance regulator (CFTR) showed a positive band at its molecular weight, approximately 170 kD. Immunostaining under confocal microscopy revealed a CFTR specific signal in the apical sections of primary conjunctival epithelial cells. In addition, RT-PCR detection amplified a cDNA fragment 100% identical to the predicted portion of the cloned rabbit CFTR message. The stage is thus set for determining the extent of CFTR contribution to cAMP-regulated Cl– conductance in pigmented rabbit conjunctival epithelial cells.Key words: conjunctiva, chloride current, CFTR, chloride channel, patch clamp, cyclic AMP, whole-cell.

An unusual voltage-gated anion channel found in the cone cells of the chicken retina

1991 ◽  
Vol 6 (1) ◽  
pp. 19-23 ◽  
Author(s):  
Martin Wilson ◽  
Evanna Gleason
Keyword(s):  
Patch Clamp ◽  
Anion Channel ◽  
Chloride Ions ◽  
Patch Clamp Technique ◽  
Adult Chicken ◽  
Voltage Gated ◽  
Cationic Current ◽  
Whole Cell Patch Clamp ◽  
Cone Cells ◽  
Inward Currents

AbstractUsing the whole-cell patch clamp technique, we have examined the voltage-gated currents present in adult chicken cone cells. When calcium and calcium-gated currents are blocked, hyperpolarizing voltage steps elicit slowly increasing inward currents as has been shown for photoreceptors in other species. Unlike the case for other species, chicken cones appear to lack the inward-rectifying cationic current Ih that contributes to the shaping of the photovoltage. Instead of Ih, these cones possess an anionic inward-rectifying current that in kinetics, activation range and probably function is remarkably similar to Ih. This anion channel is unusual in that both nitrate and acetate are more permeant than chloride ions.

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