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.

Stretch-activated channels in airway epithelial cells

1993 ◽  
Vol 265 (5) ◽  
pp. C1306-C1318 ◽  
Author(s):  
Y. K. Kim ◽  
E. R. Dirksen ◽  
M. J. Sanderson
Keyword(s):  
Epithelial Cells ◽  
Basolateral Membrane ◽  
Reversal Potential ◽  
Airway Epithelial Cells ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Airway Epithelial ◽  
Open Probability ◽  
Open States ◽  
Slow Time Constant

Two type of stretch-activated (SA) ion channels were identified in the basolateral membrane of isolated rabbit airway epithelial cells by patch-clamp techniques. Pressure activation and deactivation of one channel, which had a conductance of 29 pS, occurred after a delay of approximately 20-30 s. The open probability of this delayed stretch-activated (DSA) channel was increased from < 0.01 to 0.45 at 50 mmHg of suction. The reversal potential of the DSA channel, calculated from the pipette potential at which membrane currents reversed [-31.3 +/- 3.6 (SD) mV] and the resting membrane potential (-27.8 +/- 3.3 mV) was +3.5 +/- 3.3 mV. None of the equilibrium potentials of the ions used were similar to the calculated reversal potential of the DSA channel, suggesting that this channel is nonselective for cations. The DSA channel gating behavior was characterized by bursts of rapid transitions between open and closed states. The distribution of the open and closed times revealed that this gating behavior could be fitted with two open states and two closed states. Only the slow time constant of the closed state was decreased by suction. The second SA channel was selective for K+ and had a conductance of 65 pS but a long delay was not associated with the pressure sensitivity of this channel. The open probability of the K(+)-selective SA channel was increased from < 0.01 to 0.30 by 50 mmHg of suction. The K(+)-selective SA channel was distinct from the well-characterized basolateral K+ channel.

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 Large-conductance voltage- and Ca2+-activated K+ channel regulation by protein kinase C in guinea pig urinary bladder smooth muscle

2014 ◽  
Vol 306 (5) ◽  
pp. C460-C470 ◽  
Author(s):  
Kiril L. Hristov ◽  
Amy C. Smith ◽  
Shankar P. Parajuli ◽  
John Malysz ◽  
Georgi V. Petkov
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Guinea Pig ◽  
Bk Channels ◽  
Bk Channel ◽  
K Channel ◽  
Channel Activity ◽  
Open Probability ◽  
Channel Regulation ◽  
Pkc Activation

Large-conductance voltage- and Ca2+-activated K+ (BK) channels are critical regulators of detrusor smooth muscle (DSM) excitability and contractility. PKC modulates the contraction of DSM and BK channel activity in non-DSM cells; however, the cellular mechanism regulating the PKC-BK channel interaction in DSM remains unknown. We provide a novel mechanistic insight into BK channel regulation by PKC in DSM. We used patch-clamp electrophysiology, live-cell Ca2+ imaging, and functional studies of DSM contractility to elucidate BK channel regulation by PKC at cellular and tissue levels. Voltage-clamp experiments showed that pharmacological activation of PKC with PMA inhibited the spontaneous transient BK currents in native freshly isolated guinea pig DSM cells. Current-clamp recordings revealed that PMA significantly depolarized DSM membrane potential and inhibited the spontaneous transient hyperpolarizations in DSM cells. The PMA inhibitory effects on DSM membrane potential were completely abolished by the selective BK channel inhibitor paxilline. Activation of PKC with PMA did not affect the amplitude of the voltage-step-induced whole cell steady-state BK current or the single BK channel open probability (recorded in cell-attached mode) upon inhibition of all major Ca2+ sources for BK channel activation with thapsigargin, ryanodine, and nifedipine. PKC activation with PMA elevated intracellular Ca2+ levels in DSM cells and increased spontaneous phasic and nerve-evoked contractions of DSM isolated strips. Our results support the concept that PKC activation leads to a reduction of BK channel activity in DSM via a Ca2+-dependent mechanism, thus increasing DSM contractility.

scholarly journals Activation of Ca(2+)-dependent K+ current by acetylcholine and histamine in a human gastric epithelial cell line.

1993 ◽  
Vol 102 (4) ◽  
pp. 667-692 ◽  
Author(s):  
E Hamada ◽  
T Nakajima ◽  
S Ota ◽  
A Terano ◽  
M Omata ◽  
...  
Keyword(s):  
Membrane Potential ◽  
Epithelial Cell ◽  
Cell Line ◽  
K Channel ◽  
Resting Membrane Potential ◽  
Induced Response ◽  
Epithelial Cell Line ◽  
Bathing Solution ◽  
Pipette Solution ◽  
K Current

The effects of acetylcholine (ACh) and histamine (His) on the membrane potential and current were examined in JR-1 cells, a mucin-producing epithelial cell line derived from human gastric signet ring cell carcinoma. The tight-seal, whole cell clamp technique was used. The resting membrane potential, the input resistance, and the capacitance of the cells were approximately -12 mV, 1.4 G ohms, and 50 pF, respectively. Under the voltage-clamp condition, no voltage-dependent currents were evoked. ACh or His added to the bathing solution hyperpolarized the membrane by activating a time- and voltage-independent K+ current. The ACh-induced hyperpolarization and K+ current persisted, while the His response desensitized quickly (&lt; 1 min). These effects of ACh and His were mediated predominantly by m3-muscarinic and H1-His receptors, respectively. The K+ current induced by ACh and His was inhibited by charybdotoxin, suggesting that it is a Ca(2+)-activated K+ channel current (IK.Ca). The measurement of intracellular Ca2+ ([Ca2+]i) using Indo-1 revealed that both agents increased [Ca2+]i with similar time courses as they increased IK.Ca. When EGTA in the pipette solution was increased from 0.15 to 10 mM, the induction of IK.Ca by ACh and His was abolished. Thus, both ACh and His activate IK.Ca by increasing [Ca2+]i in JR-1 cells. In the Ca(2+)-free bathing solution (0.15 mM EGTA in the pipette), ACh evoked IK.Ca transiently. Addition of Ca2+ (1.8 mM) to the bath immediately restored the sustained IK.Ca. These results suggest that the ACh response is due to at least two different mechanisms; i.e., the Ca2+ release-related initial transient activation and the Ca2+ influx-related sustained activation of IK.Ca. Probably because of desensitization, the Ca2+ influx-related component of the His response could not be identified. Intracellularly applied inositol 1,4,5-trisphosphate (IP3), with and without inositol 1,3,4,5-tetrakisphosphate (IP4), mimicked the ACh response. IP4 alone did not affect the membrane current. Under the steady effect of IP3 or IP3 plus IP4, neither ACh nor His further evoked IK.Ca. Intracellular application of heparin or of the monoclonal antibody against the IP3 receptor, mAb18A10, inhibited the ACh and His responses in a concentration-dependent fashion. Neomycin, a phospholipase C (PLC) inhibitor, also inhibited the agonist-induced response in a concentration-dependent fashion. Although neither pertussis toxin (PTX) nor N-ethylmaleimide affected the ACh or His activation of IK,Ca, GDP beta S attenuated and GTP gamma S enhanced the agonist response.(ABSTRACT TRUNCATED AT 400 WORDS)

Na+ pump inhibition downregulates an ATP-sensitive K+ channel in rabbit proximal convoluted tubule

1993 ◽  
Vol 264 (4) ◽  
pp. F760-F764 ◽  
Author(s):  
A. M. Hurst ◽  
J. S. Beck ◽  
R. Laprade ◽  
J. Y. Lapointe
Keyword(s):  
Basolateral Membrane ◽  
Proximal Convoluted Tubule ◽  
K Channel ◽  
Bathing Solution ◽  
Channel Activity ◽  
Open Probability ◽  
Functional Link ◽  
Tightly Coupled ◽  
Stimulation Of

In several epithelial and nonepithelial tissues a functional link between the basolateral Na(+)-K(+)-adenosinetriphosphatase (Na(+)-K(+)-ATPase) and a basolateral K+ conductance has been established. However, the nature of this link is unclear. We have previously identified a K+ channel on the basolateral membrane of the proximal convoluted tubule perfused in vitro, the activity of which is increased by stimulation of Na+ transport [J. S. Beck, A. M. Hurst, J.-Y. Lapointe, and R. Laprade. Am. J. Physiol. 264 (Renal Fluid Electrolyte Physiol. 33): F496-F501, 1993]. In the present study we investigate whether basolateral membrane K+ channel activity is tightly coupled to Na(+)-K(+)-ATPase activity. In cell-attached patches (150 mM K+ pipette), following stimulation of channel activity by addition of Na(+)-cotransported solutes to the tubule lumen, mean channel open probability (NPo) was reduced from 0.35 +/- 0.09 to 0.14 +/- 0.06 (n = 7, P < 0.05) by blocking the Na(+)-K(+)-ATPase with 100 microM strophanthidin. In excised patches the channel was reversibly blocked by 2 mM ATP from the cytosolic face of the patch, such that NPo fell to 20.1 +/- 7.0% (n = 5, P < 0.001) of control and recovered to 52.2 +/- 11.2% (n = 5, P < 0.05) after washout of ATP. Diazoxide, a putative opener of ATP-sensitive K+ channels, when added to the bathing solution of an unstimulated tubule (microperfused in the absence of Na(+)-cotransported solutes), increased NPo from 0.046 +/- 0.035 to 0.44 +/- 0.2 (n = 6, P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Arachidonic acid inhibits K channels in basolateral membrane of the thick ascending limb

2002 ◽  
Vol 283 (3) ◽  
pp. F407-F414 ◽  
Author(s):  
Rui-Min Gu ◽  
Wen-Hui Wang
Keyword(s):  
Arachidonic Acid ◽  
Basolateral Membrane ◽  
Inhibitory Effect ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
K Channels ◽  
Cytochrome P 450

We have used the patch-clamp technique to study the effect of arachidonic acid (AA) on the basolateral K channels in the medullary thick ascending limb (mTAL) of rat kidney. An inwardly rectifying 50-pS K channel was identified in cell-attached and inside-out patches in the basolateral membrane of the mTAL. The channel open probability ( P o) was 0.51 at the spontaneous cell membrane potential and decreased to 0.25 by 30 mV hyperpolarization. The addition of 5 μM AA decreased channel activity, identified as NP o, from 0.58 to 0.08 in cell-attached patches. The effect of AA on the 50-pS K channel was specific because 10 μM cis-11,14,17-eicosatrienoic acid had no significant effect on channel activity. To determine whether the effect of AA was mediated by AA per se or by its metabolites, we examined the effect of AA on channel activity in the presence of indomethacin, an inhibitor of cyclooxygenase, or N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS), an inhibitor of cytochrome P-450 monooxygenase. Inhibition of cyclooxygenase increased channel activity from 0.54 to 0.9. However, indomethacin did not abolish the inhibitory effect of AA on the 50-pS K channel. In contrast, inhibition of cytochrome P-450 metabolism not only increased channel activity from 0.49 to 0.83 but also completely abolished the effect of AA. Moreover, addition of DDMS can reverse the inhibitory effect of AA on channel activity. The notion that the effect of AA was mediated by cytochrome P-450-dependent metabolites of AA is also supported by the observation that addition of 100 nM of 20-hydroxyeicosatetraenoic acid, a main metabolite of AA in the mTAL, can mimic the effect of AA. We conclude that AA inhibits the 50-pS K channel in the basolateral membrane of the mTAL and that the effect of AA is mainly mediated by cytochrome P-450-dependent metabolites of AA.

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.

scholarly journals KCNJ10 (Kir4.1) is expressed in the basolateral membrane of the cortical thick ascending limb

2015 ◽  
Vol 308 (11) ◽  
pp. F1288-F1296 ◽  
Author(s):  
Chengbiao Zhang ◽  
Lijun Wang ◽  
Xiao-Tong Su ◽  
Dao-Hong Lin ◽  
Wen-Hui Wang
Keyword(s):  
Basolateral Membrane ◽  
Reversal Potential ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Initial Part ◽  
Wild Type ◽  
Open Probability ◽  
Cell Recording ◽  
Late Part

The aim of the present study is to examine the role of Kcnj10 (Kir.4.1) in contributing to the basolateral K conductance in the cortical thick ascending limb (cTAL) using Kcnj10+/+ wild-type (WT) and Kcnj10−/− knockout (KO) mice. The patch-clamp experiments detected a 40- and an 80-pS K channel in the basolateral membrane of the cTAL. Moreover, the probability of finding the 40-pS K was significantly higher in the late part of the cTAL close to the distal convoluted tubule than those in the initial part. Immunostaining showed that Kcnj10 staining was detected in the basolateral membrane of the cTAL but the expression was not uniformly distributed. The disruption of Kcnj10 completely eliminated the 40-pS K channel but not the 80-pS K channel, suggesting the role of Kcnj10 in forming the 40-pS K channel of the cTAL. Also, the disruption of Kcnj10 increased the probability of finding the 80-pS K channel in the cTAL, especially in the late part of the cTAL. Because the channel open probability of the 80-pS K channel in KO was similar to those of WT mice, the increase in the 80-pS K channel may be achieved by increasing K channel number. The whole cell recording further showed that K reversal potential measured with 5 mM K in the bath and 140 mM K in the pipette was the same in the WT and KO mice. Moreover, Western blot and immunostaining showed that the disruption of Kcnj10 did not affect the expression of Na-K-Cl cotransporter 2 (NKCC2). We conclude that Kir.4.1 is expressed in the basolateral membrane of cTAL and that the disruption of Kir.4.1 has no significant effect on the membrane potential of the cTAL and NKCC2 expression.

scholarly journals The Ca2+-activated K+ channel and its functional roles in smooth muscle cells of guinea pig taenia coli.

1989 ◽  
Vol 94 (5) ◽  
pp. 833-847 ◽  
Author(s):  
S L Hu ◽  
Y Yamamoto ◽  
C Y Kao
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Guinea Pig ◽  
Smooth Muscle Cells ◽  
Muscle Cells ◽  
Resting Potential ◽  
K Channel ◽  
Taenia Coli ◽  
Open Probability ◽  
Open Time

Currents through single potassium channels were studied in cell-attached or inside-out patches from collagenase-dispersed smooth muscle cells of the guinea pig taenia coli. Under conditions mimicking the physiological state with [K+]i = 135 mM: [K+]o = 5.4 mM, three distinct types of K+ channel were identified with conductances around 0 mV of 147, 94, and 63 pS. The activities of the 94- and 63-pS channel were observed infrequently. The 147-pS channel was most abundant. It has a reversal potential of approximately -75 mV. It is sensitive to [Ca2+]i and to membrane potential. At -30 mV, the probability of a channel being open is at a minimum. At more positive voltages, the probability follows Boltzman distribution. A 10-fold change in [Ca2+]i causes a 25-mV negative shift of the voltage where half of the channels are open; an 11.3-mV change in membrane potential produces an e-fold increase in the probability of the channel being open when P is low. At voltages between -30 and -50 mV, the open probability increases in an anomalous manner because of a large decrease of the channel closed time without much change in the channel open time. This anomalous activity may play a regulatory role in maintaining the resting potential. The histograms of channel open and closed time fit well, respectively, with single and double exponential distributions. Upon step depolarizations by 100-ms pulses, the 147-pS channel opens with a brief delay. The delay shortens and both the number of open channels and the open time increase with increasing positivity of the potential. The averaged currents during the step depolarizations closely resemble the delayed rectifying outward K+ currents in whole-cell recordings.

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