scholarly journals Secretory activation of basolateral membrane Cl−channels in guinea pig distal colonic crypts

2003 ◽  
Vol 284 (4) ◽  
pp. C918-C933 ◽  
Author(s):  
Yingjun Li ◽  
Susan Troutman Halm ◽  
Dan R. Halm
Keyword(s):  
Guinea Pig ◽  
Relative Permeability ◽  
Single Channel ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Resting Membrane Potential ◽  
Colonic Crypts ◽  
Voltage Dependent ◽  
Cl Channels ◽  
Excised Patches

Cell-attached recordings revealed Cl− channel activity in basolateral membrane of guinea pig distal colonic crypts isolated from basement membrane. Outwardly rectified currents (gpClor) were apparent with a single-channel conductance (γ) of 29 pS at resting membrane electrical potential; another outward rectifier with γ of 24 pS was also observed (∼25% of gpClor). At a holding potential of −80 mV γ was 18 pS for bothgpClor currents, and at +80 mV γ was 67 and 40 pS, respectively. Identity as Cl− channels was confirmed in excised patches by changing bath ion composition. From reversal potentials, relative permeability of K+ over Cl− ( P K/ P Cl) was 0.07 ± 0.03, with relative permeability of Na+over Cl−( P Na/ P Cl) = 0.08 ± 0.04. A second type of Cl− channel was seen with linear current-voltage ( I-V) relations (gpClL), having subtypes with γ of 21, 13, and 8 pS. Epinephrine or forskolin increased the number of opengpClor and gpClL. Open probabilities ( P o) ofgpClor, gpClL21, andgpClL13 were voltage dependent in cell-attached patches, higher at more positive potentials. Kinetics ofgpClor were more rapid with epinephrine activation than with forskolin activation. Epinephrine increased P o at the resting membrane potential forgpClL13. Secretagogue activation of these Cl− channels may contribute to stimulation of electrogenic K+ secretion across colonic epithelium by increasing basolateral membrane Cl− conductance that permits Cl− exit after uptake via Na+-K+-2Cl− cotransport.

scholarly journals Secretory modulation of basolateral membrane inwardly rectified K+ channel in guinea pig distal colonic crypts

2002 ◽  
Vol 282 (4) ◽  
pp. C719-C735 ◽  
Author(s):  
Yingjun Li ◽  
Dan R. Halm
Keyword(s):  
Guinea Pig ◽  
Basolateral Membrane ◽  
Inward Rectifier ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Prostaglandin E ◽  
Open Probability ◽  
Pipette Solution ◽  
Colonic Crypts ◽  
Activity Mode

Cell-attached recordings revealed K+ channel activity in basolateral membranes of guinea pig distal colonic crypts. Inwardly rectified currents were apparent with a pipette solution containing 140 mM K+. Single-channel conductance (γ) was 9 pS at the resting membrane potential. Another inward rectifier with γ of 19 pS was observed occasionally. At a holding potential of −80 mV, γ was 21 and 41 pS, respectively. Identity as K+ channels was confirmed after patch excision by changing the bath ion composition. From reversal potentials, relative permeability of Na+ over K+ ( P Na/ P K) was 0.02 ± 0.02, with P Rb/ P K = 1.1 and P Cl/ P K < 0.03. Spontaneous open probability ( P o) of the 9-pS inward rectifier (gpKir) was voltage independent in cell-attached patches. Both a low ( P o = 0.09 ± 0.01) and a moderate ( P o = 0.41 ± 0.01) activity mode were observed. Excision moved gpKir to the medium activity mode; P o ofgpKir was independent of bath Ca2+activity and bath acidification. Addition of Cl− and K+ secretagogues altered P o ofgpKir. Forskolin or carbachol (10 μM) activated the small-conductance gpKir in quiescent patches and increased P o in low-activity patches. K+ secretagogues, either epinephrine (5 μM) or prostaglandin E2 (100 nM), decreased P o of gpKir in active patches. This gpKir may be involved in electrogenic secretion of Cl− and K+ across the colonic epithelium, which requires a large basolateral membrane K+ conductance during maximal Cl− secretion and, presumably, a lower K+ conductance during primary electrogenic K+ secretion.

Double-barreled chloride channels of collecting duct basolateral membrane

1990 ◽  
Vol 259 (1) ◽  
pp. F46-F52 ◽  
Author(s):  
S. C. Sansom ◽  
B. Q. La ◽  
S. L. Carosi
Keyword(s):  
Chloride Channels ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Electric Organ ◽  
Cortical Collecting Duct ◽  
Cl Channel ◽  
Voltage Dependent ◽  
Cl Channels ◽  
Excised Patches ◽  
High Concentrations

Microelectrode studies have shown that the basolateral membrane of the principal cells (PC) of the rabbit cortical collecting duct (CCD) contains Cl(-)-conductive pathways. To determine the properties of single Cl- channels we prepared the basolateral membrane for patch clamping by incubating the CCD in collagenase and/or tearing the basement membrane with a fine needle. When high concentrations of collagenase were used, only a small nonselective channel was observed. In low concentrations or the absence of collagenase, however, we identified a Cl- channel (g46) in both cell-attached and excised patches. The Cl- channel gated rapidly between three equally spaced substates of 0 (S0), 23 (S1), and 46 pS (S2) and slowly between states C (inactive) and S0. The conductance of each substate was not voltage dependent between pipette potentials from -60 to +60 mV (cell attached). The probability that the channel gated from C to S0 increased with hyperpolarizing potentials, but the probability that g46 was in substate S0 increased with depolarizing patch potentials. This channel was similar to that described by Miller for the nonexcitable membrane of the electric organ of Torpedo californica. Because g46 was the most frequently observed basolateral membrane channel and was voltage dependent at physiological potentials, it is probably the channel responsible for the dominant Cl- conductance of PC.

Basolateral potassium channels in renal proximal tubule

1987 ◽  
Vol 253 (3) ◽  
pp. F476-F487 ◽  
Author(s):  
H. Sackin ◽  
L. G. Palmer
Keyword(s):  
Single Channel ◽  
Basolateral Membrane ◽  
K Channel ◽  
Channel Conductance ◽  
Single Channel Conductance ◽  
K Channels ◽  
Open Time ◽  
Excised Patches ◽  
The Mean ◽  
Inside Out

Potassium (K+) channels in the basolateral membrane of unperfused Necturus proximal tubules were studied in both cell-attached and excised patches, after removal of the tubule basement membrane by manual dissection without collagenase. Two different K+ channels were identified on the basis of their kinetics: a short open-time K+ channel, with a mean open time less than 1 ms, and a long open-time K+ channel with a mean open time greater than 20 ms. The short open-time channel occurred more frequently than the longer channel, especially in excised patches. For inside-out excised patches with Cl- replaced by gluconate, the current-voltage relation of the short open-time K+ channel was linear over +/- 60 mV, with a K+-Na+ selectivity of 12 +/- 2 (n = 12), as calculated from the reversal potential with oppositely directed Na+ and K+ gradients. With K-Ringer in the patch pipette and Na-Ringer in the bath, the conductance of the short open-time channel was 47 +/- 2 pS (n = 15) for cell-attached patches, 26 +/- 2 pS (n = 15) for patches excised (inside out) into Na-Ringer, and 36 +/- 6 pS (n = 3) for excised patches with K-Ringer on both sides. These different conductances can be partially explained by a dependence of single-channel conductance on the K+ concentration on the interior side of the membrane. In experiments with a constant K+ gradient across excised patches, large changes in Na+ at the interior side of the membrane produced no change in single-channel conductance, arguing against a direct block of the K+ channel by Na+. Finally, the activity of the short open-time channel was voltage gated, where the mean number of open channels decreased as a linear function of basolateral membrane depolarization for potentials between -60 and 0 mV. Depolarization from -60 to -40 mV decreased the mean number of open K+ channels by 28 +/- 8% (n = 6).

Rectification of muscarinic K+ current by magnesium ion in guinea pig atrial cells

1987 ◽  
Vol 253 (1) ◽  
pp. H210-H214
Author(s):  
M. Horie ◽  
H. Irisawa
Keyword(s):  
Guinea Pig ◽  
Action Potentials ◽  
Single Channel ◽  
Outward Current ◽  
Atrial Cells ◽  
Voltage Dependent ◽  
K Current ◽  
Single Channel Currents ◽  
Channel Currents ◽  
Low K

Rectifying properties of the acetylcholine (ACh)-sensitive K+ channels were studied using a patch-clamp method in single atrial cells prepared enzymatically from adult guinea pig hearts. In the presence of micromolar concentration of nonhydrolyzable guanosine 5'-triphosphate (GTP) analogue 5'-guanylylimidodiphosphate (GppNHp) and the absence of Mg2+ at the inner surface of patch membrane [( Mg2+]i), the channel activity recovered in inside-out patch condition. The single channel conductance became ohmic between -80 and +80 mV (symmetrical 150 mM K+ solutions). The rapid relaxation of outward single channel currents was disclosed on a depolarization. [Mg2+]i blocked the outward current through the channel dose- and voltage-dependently and also induced a dose-dependent increase in the channel activation. The apparent paradoxical role of [Mg2+]i is important for the cholinergic control in the heart; voltage-dependent Mg block ensures a low K+ conductance of cell membrane at the plateau of action potentials during the exposure to ACh, thereby slowing the heart rate without unfavorable shortening of the action potentials.

Two types of voltage-dependent potassium channels in outer hair cells from the guinea pig cochlea

1999 ◽  
Vol 277 (5) ◽  
pp. C913-C925 ◽  
Author(s):  
Thierry van den Abbeele ◽  
Jacques Teulon ◽  
Patrice Tran Ba Huy
Keyword(s):  
Guinea Pig ◽  
Hair Cells ◽  
Basolateral Membrane ◽  
Outer Hair Cells ◽  
Catalytic Subunit ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Guinea Pig Cochlea ◽  
Voltage Dependent ◽  
Inside Out

Cell-attached and cell-free configurations of the patch-clamp technique were used to investigate the conductive properties and regulation of the major K+channels in the basolateral membrane of outer hair cells freshly isolated from the guinea pig cochlea. There were two major voltage-dependent K+ channels. A Ca2+-activated K+ channel with a high conductance (220 pS, P K/ P Na= 8) was found in almost 20% of the patches. The inside-out activity of the channel was increased by depolarizations above 0 mV and increasing the intracellular Ca2+concentration. External ATP or adenosine did not alter the cell-attached activity of the channel. The open probability of the excised channel remained stable for several minutes without rundown and was not altered by the catalytic subunit of protein kinase A (PKA) applied internally. The most frequent K+ channel had a low conductance and a small outward rectification in symmetrical K+ conditions (10 pS for inward currents and 20 pS for outward currents, P K/ P Na= 28). It was found significantly more frequently in cell-attached and inside-out patches when the pipette contained 100 μM acetylcholine. It was not sensitive to internal Ca2+, was inhibited by 4-aminopyridine, was activated by depolarization above −30 mV, and exhibited a rundown after excision. It also had a slow inactivation on ensemble-averaged sweeps in response to depolarizing pulses. The cell-attached activity of the channel was increased when adenosine was superfused outside the pipette. This effect also occurred with permeant analogs of cAMP and internally applied catalytic subunit of PKA. Both channels could control the cell membrane voltage of outer hair cells.

Voltage-dependent K+ current in capillary endothelial cells isolated from guinea pig heart

1999 ◽  
Vol 277 (1) ◽  
pp. H119-H127 ◽  
Author(s):  
Michael Dittrich ◽  
Jürgen Daut
Keyword(s):  
Guinea Pig ◽  
Time Course ◽  
Single Channel ◽  
Patch Clamp Technique ◽  
Guinea Pig Heart ◽  
Potential Oscillations ◽  
Time To Peak ◽  
Voltage Dependent ◽  
Capillary Endothelial Cells ◽  
Single Channel Currents

Capillary fragments were isolated from guinea pig hearts, and their electrical properties were studied using the perforated-patch and cell-attached mode of the patch-clamp technique. A voltage-dependent K+ current was discovered that was activated at potentials positive to −20 mV and showed a sigmoid rising phase. For depolarizing voltage steps from −128 to +52 mV, the time to peak was 71 ± 5 ms (mean ± SE) and the amplitude of the current was 3.7 ± 0.5 pA/pF in the presence of 5 mM external K+. The time course of inactivation was exponential with a time constant of 7.2 ± 0.5 s at +52 mV. The current was blocked by tetraethylammonium (inhibitory constant ∼3 mM) but was not affected by charybdotoxin (1 μM) or apamin (1 μM). In the cell-attached mode, depolarization-activated single-channel currents were found that inactivated completely within 30 s; the single-channel conductance was 12.3 ± 2.4 pS. The depolarization-activated K+current described here may play a role in membrane potential oscillations of the endothelium.

scholarly journals A chloride channel from lobster walking leg nerves. Characterization of single-channel properties in planar bilayers.

1990 ◽  
Vol 96 (4) ◽  
pp. 707-733 ◽  
Author(s):  
G L Lukács ◽  
E Moczydlowski
Keyword(s):  
Single Channel ◽  
Disulfonic Acid ◽  
Ph Change ◽  
Planar Bilayers ◽  
Voltage Range ◽  
Cl Channel ◽  
Voltage Dependent ◽  
Cl Channels ◽  
Transport Inhibitors ◽  
Small Conductance

A novel, small conductance of Cl- channel was characterized by incorporation into planar bilayers from a plasma membrane preparation of lobster walking leg nerves. Under conditions of symmetrical 100 mM NaCl, 10 mM Tris-HCl, pH 7.4, single Cl- channels exhibit rectifying current-voltage (I-V) behavior with a conductance of 19.2 +/- 0.8 pS at positive voltages and 15.1 +/- 1.6 pS in the voltage range of -40 to 0 mV. The channel exhibits a negligible permeability for Na+ compared with Cl- and displays the following sequence of anion permeability relative to Cl- as measured under near bi-ionic conditions: I- (2.7) greater than NO3- (1.8) greater than Br- (1.5) greater than Cl- (1.0) greater than CH3CO2- (0.18) greater than HCO3- (0.10) greater than gluconate (0.06) greater than F- (0.05). The unitary conductance saturates with increasing Cl- concentration in a Michaelis-Menten fashion with a Km of 100 mM and gamma max = 33 pS at positive voltage. The I-V curve is similar in 10 mM Tris or 10 mM HEPES buffer, but substitution of 100 mM NaCl with 100 mM tetraethylammonium chloride on the cis side results in increased rectification with a 40% reduction in current at negative voltages. The gating of the channel is weakly voltage dependent with an open-state probability of 0.23 at -75 mV and 0.64 at +75 mV. Channel gating is sensitive to cis pH with an increased opening probability observed for a pH change of 7.4 to 11 and nearly complete inhibition for a pH change of 7.4 to 6.0. The lobster Cl- channel is reversibly blocked by the anion transport inhibitors, SITS (4-acetamido, 4'-isothiocyanostilbene-2,2'-disulfonic acid) and NPPB (5-nitro-2-(3-phenylpropylamino)benzoic acid). Many of these characteristics are similar to those previously described for small conductance Cl- channels in various vertebrate cells, including epithelia. These functional comparisons suggest that this invertebrate Cl- channel is an evolutionary prototype of a widely distributed class of small conductance anion channels.

scholarly journals Characterization of the calcium-activated chloride channel in isolated guinea-pig hepatocytes.

1994 ◽  
Vol 104 (2) ◽  
pp. 357-373 ◽  
Author(s):  
S Koumi ◽  
R Sato ◽  
T Aramaki
Keyword(s):  
Guinea Pig ◽  
Single Channel ◽  
Hill Coefficient ◽  
Disulfonic Acid ◽  
Dependent Manner ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Whole Cell ◽  
Cl Channels ◽  
Inside Out

Macroscopic and unitary currents through Ca(2+)-activated Cl- channels were examined in enzymatically isolated guinea-pig hepatocytes using whole-cell, excised outside-out and inside-out configurations of the patch-clamp technique. When K+ conductances were blocked and the intracellular Ca2+ concentration ([Ca2+]i) was set at 1 microM (pCa = 6), membrane currents were observed under whole-cell voltage-clamp conditions. The reversal potential of the current shifted by approximately 60 mV per 10-fold change in the external Cl- concentration. In addition, the current did not appear when Cl- was omitted from the internal and external solutions, indicating that the current was Cl- selective. The current was activated by increasing [Ca2+]i and was inactivated in Ca(2+)-free, 5 mM EGTA internal solution (pCa &gt; 9). The current was inhibited by bath application of 9-anthracenecarboxylic acid (9-AC) and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid (DIDS) in a voltage-dependent manner. In single channel recordings from outside-out patches, unitary current activity was observed, whose averaged slope conductance was 7.4 +/- 0.5 pS (n = 18). The single channel activity responded to extracellular Cl- changes as expected for a Cl- channel current. The open time distribution was best described by a single exponential function with mean open lifetime of 97.6 +/- 10.4 ms (n = 11), while at least two exponentials were required to fit the closed time distributions with a time constant for the fast component of 21.5 +/- 2.8 ms (n = 11) and that for the slow component of 411.9 +/- 52.0 ms (n = 11). In excised inside-out patch recordings, channel open probability was sensitive to [Ca2+]i. The relationship between [Ca2+]i and channel activity was fitted by the Hill equation with a Hill coefficient of 3.4 and the half-maximal activation was 0.48 microM. These results suggest that guinea-pig hepatocytes possess Ca(2+)-activated Cl- channels.

A novel GABAergic action mediated by functional coupling between GABAB-like receptor and two different high-conductance K+ channels in cricket Kenyon cells

2013 ◽  
Vol 109 (7) ◽  
pp. 1735-1745 ◽  
Author(s):  
Atsunao Nakamura ◽  
Masami Yoshino
Keyword(s):  
Single Channel ◽  
Firing Frequency ◽  
Resting Membrane Potential ◽  
Functional Coupling ◽  
Coupling Mechanism ◽  
Open Probability ◽  
Kenyon Cells ◽  
Voltage Dependent ◽  
Patch Configuration ◽  
High Conductance

The γ-aminobutyric acid type B (GABAB) receptor has been shown to attenuate high-voltage-activated Ca2+ currents and enhance voltage-dependent or inwardly rectifying K+ currents in a variety of neurons. In this study, we report a novel coupling of GABAB-like receptor with two different high-conductance K+ channels, Na+-activated K+ (KNa) channel and Ca2+-activated K+ (KCa) channel, in Kenyon cells isolated from the mushroom body of the cricket brain. Single-channel activities of KNa and KCa channels in response to bath applications of GABA and the GABAB-specific agonist SKF97541 were recorded with the cell-attached patch configuration. The open probability ( Po) of both KNa and KCa channels was found to be increased by bath application of GABA, and this increase in Po was antagonized by coapplication of the GABAB antagonist CGP54626, suggesting that GABAB-like receptors mediate these actions. Similarly, GABAB-specific agonist SKF97541 increased the Po of both KNa and KCa channels. Perforated-patch recordings using β-escin further revealed that SKF97541 increased the amplitude of the outward currents elicited by step depolarizations. Under current-clamp conditions, SKF97541 decreased the firing frequency of spontaneous action potential (AP) and changed the AP waveform. The amplitude and duration of AP were decreased, whereas the afterhyperpolarization of AP was increased. Resting membrane potential, however, was not significantly altered by SKF97541. Taken together, these results suggest that GABAB-like receptor is functionally coupled with both KNa and KCa channels and this coupling mechanism may serve to prevent AP formation and limit excitatory synaptic input.

Basolateral outward rectifier chloride channel in isolated crypts of mouse colon

2000 ◽  
Vol 279 (2) ◽  
pp. G277-G287 ◽  
Author(s):  
Olivier Mignen ◽  
Stéphane Egee ◽  
Martine Liberge ◽  
Brian J. Harvey
Keyword(s):  
Protein Kinase ◽  
Chloride Channels ◽  
Single Channel ◽  
Basolateral Membrane ◽  
Distal Colon ◽  
Open Probability ◽  
Voltage Dependent ◽  
Intracellular Ca ◽  
Dependent Protein ◽  
Inside Out

Single channel patch-clamp techniques were used to demonstrate the presence of outwardly rectifying chloride channels in the basolateral membrane of crypt cells from mouse distal colon. These channels were rarely observed in the cell-attached mode and, in the inside-out configuration, only became active after a delay and depolarizing voltage steps. Single channel conductance was 23.4 pS between −100 and −40 mV and increased to 90.2 pS between 40 and 100 mV. The channel permeability sequence for anions was: I− > SCN− > Br−> Cl− > NO3 − > F−≫ SO4 2− ≈ gluconate. In inside-out patches, the channel open probability was voltage dependent but insensitive to intracellular Ca2+ concentration. In cell-attached mode, forskolin, histamine, carbachol, A-23187, and activators of protein kinase C all failed to activate the channel, and activity could not be evoked in inside-out patches by exposure to the purified catalytic subunit of cAMP-dependent protein kinase A. The channel was inhibited by 5-nitro-2-(3-phenylpropylamino)benzoate, 9-anthracenecarboxylic acid, and DIDS. Stimulation of G proteins with guanosine 5′- O-(3-thiotriphosphate) decreased the channel open probability and conductance, whereas subsequent addition of guanosine 5′- O-(2-thiodiphosphate) reactivated the channel.

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