Cation channels in basolateral membranes of sheep parotid secretory cells

1992 ◽  
Vol 263 (5) ◽  
pp. G786-G794 ◽  
Author(s):  
E. A. Wegman ◽  
T. Ishikawa ◽  
J. A. Young ◽  
D. I. Cook
Keyword(s):  
Membrane Potential ◽  
Relative Permeability ◽  
Basolateral Membrane ◽  
Cation Channels ◽  
K Channel ◽  
Secretory Cells ◽  
K Channels ◽  
Basolateral Membranes ◽  
Sheep Parotid ◽  
Relative Conductance

We observed 240-pS K+ channels in 63% of cell-attached patches, and 30-pS K+ channels were observed in 95% of cell-attached patches. The 240-pS K+ channel had the relative permeability sequence of K+ (1) = Rb+ (1) > Cs+ (0.3) >> Na+ (0.03) and the relative conductance sequence of K+ (1) > Rb+ (0.22) > Cs+ (0.05) > Na+ (0). It was activated by intracellular free Ca2+ and by depolarization. It was blocked by 10 mmol/l tetraethylammonium (TEA) applied extracellularly. The 30-pS K+ channel had the relative permeability sequence of K+ (1) = Rb+ (1) > Cs+ (> Na+ (< 0.09) and the relative conductance sequence of K+ (1) > Rb+ (0.45) > Cs+ (0) = Na+ (0). Its activity was not sensitive to cytosolic free Ca2+ or membrane potential, and it was not blocked by 10 mmol/l TEA extracellularly. Acetylcholine (10 mumol/l) activated the 240-pS voltage-activated and Ca(2+)-activated K+ channels but did not activate the 30-pS K+ channels. We conclude that the 30-pS K+ channel probably determines the properties of the basolateral membrane in unstimulated sheep parotid secretory cells, whereas the 240-pS voltage-activated and Ca(2+)-activated K+ channel may be important during parasympathomimetic stimulation.

scholarly journals K+ reabsorption by the lower Malpighian tubule of Rhodnius prolixus: inhibition by Ba2+ and blockers of H+/K+-ATPases

1997 ◽  
Vol 200 (1) ◽  
pp. 139-147 ◽  
Author(s):  
C Haley ◽  
M Donnell
Keyword(s):  
Membrane Potential ◽  
Gastric Mucosa ◽  
Channel Blocker ◽  
Basolateral Membrane ◽  
Malpighian Tubule ◽  
Blood Feeding ◽  
Rhodnius Prolixus ◽  
K Channel ◽  
Bafilomycin A1 ◽  
K Channels

Active K+ reabsorption by the lower Malpighian tubule of the blood-feeding hemipteran Rhodnius prolixus does not involve the amiloride-sensitive K+/H+ exchangers or V-type H+-ATPases implicated in secretion of ions from haemolymph to lumen in the upper tubule. Amiloride, N-ethylmaleimide, 4-chloro-7-nitrobenzo-2-oxa-1,3-diazol and bafilomycin A1 inhibit haemolymph-to-lumen secretion of Na+ and K+ by the upper Malpighian tubule, but have little or no effect on lumen-to-haemolymph reabsorption of K+ by the lower tubule. The effects of inhibitors of H+/K+-ATPases, including omeprazole and SCH 28080, suggest that a pump similar to the H+/K+-ATPase of the gastric mucosa is involved in KCl reabsorption. The presence of K+ channels in the basolateral membrane in the lower Malpighian tubule is suggested by inhibition of KCl reabsorption by basolateral but not apical application of the K+ channel blocker Ba2+, and by blockade of K+-dependent changes in membrane potential by Ba2+. It is proposed, therefore, that K+ is pumped from lumen to cell by an ATP-dependent pump resembling the H+/K+-ATPase of the gastric mucosa, and that K+ leaks from cell to bathing saline (haemolymph) via an electrodiffusive pathway (i.e. K+ channels).

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).

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.

Adenosine stimulates the basolateral 50 pS K channels in the thick ascending limb of the rat kidney

2007 ◽  
Vol 293 (1) ◽  
pp. F299-F305 ◽  
Author(s):  
Ruimin Gu ◽  
Jing Wang ◽  
Yunhong Zhang ◽  
Wennan Li ◽  
Ying Xu ◽  
...  
Keyword(s):  
Adenosine Receptor ◽  
Rat Kidney ◽  
Basolateral Membrane ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Dependent Manner ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
K Channels ◽  
Adenosine Receptor Agonist

We used the patch-clamp technique to examine the effect of adenosine on the basolateral K channels in the thick ascending limb (TAL) of the rat kidney. A 50-pS inwardly rectifying K channel was detected in the basolateral membrane, and the channel activity was decreased by hyperpolarization. Application of adenosine (10 μM) increased the activity of basolateral 50 pS K channels, defined by NPo, from 0.21 to 0.41. The effect of adenosine on the 50 pS K channels was mimicked by cyclohexyladenosine (CHA), which increased channel activity by a dose-dependent manner. However, inhibition of the A1 adenosine receptor with 8-cyclopentyl-1, 3-dipropylxanthine (DPCPX) failed to block the effect of CHA. In contrast, application of 8-(3-chlorostyryl) caffeine (CSC), an A2 adenosine antagonist, abolished the stimulatory effect of CHA. The possibility that the effect of adenosine and adenosine analog on the basolateral 50 pS K channel was the result of activation of the A2 adenosine receptor was also suggested by the observation that application of CGS-21680, a selected A2A adenosine receptor agonist, increased the channel activity. Also, inhibition of PKA with N-[2-(methylamino)ethyl]-5-isoquinoline sulfonamide-2HC1 abolished the stimulatory effect of CHA on the basolateral 50 pS K channel. Moreover, addition of the membrane-permeable cAMP analog increases the activity of 50 pS K channels. We conclude that adenosine activates the 50 pS K channel in the basolateral membrane of the TAL and the stimulatory effect is mainly mediated by a PKA-dependent pathway via the A2 adenosine receptor in the TAL.

scholarly journals Messenger-mediated control of potassium channels in secretory cells

1986 ◽  
Vol 124 (1) ◽  
pp. 33-52
Author(s):  
O. H. Petersen ◽  
I. Findlay ◽  
K. Suzuki ◽  
M. J. Dunne
Keyword(s):  
Plasma Membrane ◽  
Pancreatic Beta Cells ◽  
Acinar Cells ◽  
Direct Access ◽  
K Channel ◽  
Secretory Cells ◽  
Single Channels ◽  
Intact Cells ◽  
Membrane Area ◽  
K Channels

In exocrine acinar cells (pancreas, salivary gland, lacrimal gland) stimulation with hormones or neurotransmitters evokes K+ loss due to opening of K+ channels in the plasma membrane whereas in the insulin-secreting pancreatic beta-cells, stimulation with glucose or glyceraldehyde evokes membrane depolarization due to closure of K+ channels. By measuring directly the small K+ currents flowing through single channels, in electrically isolated patches of plasma membrane of intact cells, it can be shown that stimulants having no direct access to the small membrane area from which recording is made can influence the pattern of channel opening. In the case of hormonal activation of exocrine acinar cells, Ca2+ is the final messenger and the K+-selective channel involved in the response has a high unit conductance, is very voltage sensitive and can be blocked by external tetraethylammonium. In the case of the insulin-secreting cells, the K+ channel which is inhibited by metabolic stimulation is a voltage-insensitive, inward rectifier which can be blocked by quinine. In experiments on permeabilized cells or cell-free excised, inside-out, membrane patches it can be shown that ATP evokes channel closure and ATP produced by glycolysis may therefore function as the internal messenger.

Basolateral K+ channels in airway epithelia. I. Regulation by Ca2+ and block by charybdotoxin

1990 ◽  
Vol 258 (6) ◽  
pp. L334-L342 ◽  
Author(s):  
J. D. McCann ◽  
J. Matsuda ◽  
M. Garcia ◽  
G. Kaczorowski ◽  
M. J. Welsh
Keyword(s):  
Recent Observation ◽  
Basolateral Membrane ◽  
Airway Epithelial Cells ◽  
K Channel ◽  
Ionophore A23187 ◽  
Airway Epithelial ◽  
Airway Epithelia ◽  
K Channels ◽  
Cl Channels ◽  
Inwardly Rectifying

In airway epithelia, adenosine 3',5'-cyclic monophosphate (cAMP) stimulates Cl- secretion by activating apical membrane Cl- channels and basolateral membrane K+ channels. Cl- channels are regulated by cAMP-dependent phosphorylation, whereas K+ channels are regulated by the cytosolic Ca2+ concentration, [Ca2+]c. Our recent observation that cAMP increases [Ca2+]c suggested that cAMP might indirectly regulate K+ channels by increasing [Ca2+]c. To study regulation of K+ channels we measured 86Rb efflux, single K+ channels in membrane patches, and [Ca2+]c with the fluorescent indicator fura-2. Isoproterenol and Ca2+ ionophore, A23187, transiently increased [Ca2+]c and transiently stimulated 86Rb efflux. Stimulation of 86Rb efflux resulted from release of intracellular Ca2+ stores. 86Rb efflux was blocked by Ba2+ or charybdotoxin, but not by tetraethylammonium. Charybdotoxin prevented all of the 86Rb efflux that was stimulated by A23187 or by forskolin. Charybdotoxin also blocked the low-conductance inwardly rectifying K+ channel (KCLIC) in membrane patches. These results indicate that the KCLIC channel is responsible for the Ca2(+)-dependent increase in K+ permeability in airway epithelial cells. They also indicate that cAMP-induced release of intracellular Ca2+ is sufficient to activate K+ channels.

P2 purinoceptors regulate calcium-activated chloride and fluid transport in 31EG4 mammary epithelia

2003 ◽  
Vol 284 (4) ◽  
pp. C897-C909 ◽  
Author(s):  
Sasha Blaug ◽  
Jodi Rymer ◽  
Stephen Jalickee ◽  
Sheldon S. Miller
Keyword(s):  
Membrane Potential ◽  
Fluid Transport ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Fluid Secretion ◽  
Extracellular Nucleotides ◽  
Basolateral Membranes ◽  
Apical Side ◽  
Mammary Epithelia

It has been reported that secretory mammary epithelial cells (MEC) release ATP, UTP, and UDP upon mechanical stimulation. Here we examined the physiological changes caused by ATP/UTP in nontransformed, clonal mouse mammary epithelia (31EG4 cells). In control conditions, transepithelial potential (apical side negative) and resistance were −4.4 ± 1.3 mV (mean ± SD, n = 12) and 517.7 ± 39.4 Ω · cm2, respectively. The apical membrane potential was −43.9 ± 1.7 mV, and the ratio of apical to basolateral membrane resistance ( R A/ R B) was 3.5 ± 0.2. Addition of ATP or UTP to the apical or basolateral membranes caused large voltage and resistance changes with an EC50 of ∼24 μM (apical) and ∼30 μM (basal). Apical ATP/UTP (100 μM) depolarized apical membrane potential by 17.6 ± 0.8 mV ( n = 7) and decreased R A/ R B by a factor of ≈3. The addition of adenosine to either side (100 μM) had no effect on any of these parameters. The ATP/UTP responses were partially inhibited by DIDS and suramin and mediated by a transient increase in free intracellular Ca2+ concentration (427 ± 206 nM; 15–25 μM ATP, apical; n = 6). This Ca2+ increase was blocked by cyclopiazonic acid, by BAPTA, or by xestospongin C. 31EG4 MEC monolayers also secreted or absorbed fluid in the resting state, and ATP or UTP increased fluid secretion by 5.6 ± 3 μl · cm−2 · h−1( n = 10). Pharmacology experiments indicate that 31EG4 epithelia contain P2Y2 purinoceptors on the apical and basolateral membranes, which upon activation stimulate apical Ca2+-dependent Cl channels and cause fluid secretion across the monolayer. This suggests that extracellular nucleotides could play a fundamental role in mammary gland paracrine signaling and the regulation of milk composition in vivo.

Basolateral K+ channels in airway epithelia. II. Role in Cl- secretion and evidence for two types of K+ channel

1990 ◽  
Vol 258 (6) ◽  
pp. L343-L348 ◽  
Author(s):  
J. D. McCann ◽  
M. J. Welsh
Keyword(s):  
Epithelial Cells ◽  
Time Course ◽  
Basolateral Membrane ◽  
Airway Epithelial Cells ◽  
K Channel ◽  
Airway Epithelial ◽  
K Channels ◽  
Cl Secretion ◽  
Transient Component ◽  
Permeable Supports

We previously described a Ca2(+)-activated K+ channel (KCLIC) in airway epithelial cells [J. D. McCann, J. Matsuda, M. Garcia, G. Kaczorowski, and M. J. Welsh. Am. J. Physiol 258 (Lung Cell. Mol. Physiol. 2): L334-L342, 1990]. To determine whether the KCLIC channel is a basolateral membrane channel and to understand its role in Cl- secretion, we studied airway epithelial cells grown on permeable supports. When cells were stimulated with A23187, charybdotoxin (ChTX) inhibited Cl- secretion and 86Rb efflux at the same concentrations, indicating that the KCLIC channel is required for Ca2(+)-stimulated Cl- secretion. We also investigated the function of K+ channels in adenosine 3',5'-cyclic monophosphate-stimulated secretion. Addition of isoproterenol caused a biphasic increase in Cl- secretion; the time course of the transient component correlated with the time course of the isoproterenol-induced increase in Ca2+ concentration [( Ca2+]c). ChTX inhibited the transient component, but not the prolonged component of secretion; Ba2+ inhibited the sustained component. These results suggest that when cells are grown on permeable supports isoproterenol-induced secretion depends on activation of two types of K+ channel: the KCLIC channel that is stimulated initially and a ChTX-insensitive K+ channel that is stimulated during sustained secretion. This conclusion was supported by measurement of 86Rb efflux from cell monolayers

Identification of a Basolateral Membrane Potassium Channel from Teleost Intestinal Epithelial Cells

1991 ◽  
Vol 159 (1) ◽  
pp. 45-64
Author(s):  
CHRISTOPHER A. LORETZ ◽  
CHARLES R. FOURTNER
Keyword(s):  
Membrane Potential ◽  
Epithelial Cells ◽  
Intestinal Epithelial Cells ◽  
Basolateral Membrane ◽  
K Channel ◽  
Ca Channel ◽  
Intestinal Epithelial ◽  
Channel Activity ◽  
Open Probability ◽  
Physiological Range

Using patch-clamp techniques, a Ca2+-dependent, voltage-gated K+ channel [K(Ca) channel] was isolated from the basolateral membrane of NaCl-absorbing intestinal epithelial cells of the goby Gillichthys mirabilis. This K(Ca) channel had a high conductance (approximately 150 pS) in the physiological range of membrane potential. Conclusive identification as a K+ channel is supported by dependence of the reversal potential for single-channel current on the K+ concentration gradient and the ability of Ba2+, Cs+ and other pharmacological agents to block the channel. The channel was highly selective for K+ over Na+ (PNa/PK=0.04). Channel activity, expressed as open probability (Po), was dependent on membrane potential with depolarization increasing Po over the physiological range in the presence of Ca2+. Channel activity was also dependent on cytoplasmic-side Ca2+. Po was reduced to near-zero levels following EGTA chelation of Ca2+ in the solution bathing the cytoplasmic face of excised membrane patches; channel activity was most sensitive to changes in Ca2+ concentration between 10nmoll−1 and 10μmoll−1. This K(Ca) channel may be one of several avenues for K+ exit across the basolateral cell membrane and, as such, may play roles in both transepithelial salt transport and maintenance of intracellular ionic composition.

scholarly journals Apical K+ channels in Necturus taste cells. Modulation by intracellular factors and taste stimuli.

1992 ◽  
Vol 99 (4) ◽  
pp. 591-613 ◽  
Author(s):  
T A Cummings ◽  
S C Kinnamon
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Taste Receptor ◽  
K Channel ◽  
Patch Clamp Recording ◽  
Open Probability ◽  
K Channels ◽  
Voltage Dependent ◽  
Whole Cell Recordings ◽  
Inside Out

The apically restricted, voltage-dependent K+ conductance of Necturus taste receptor cells was studied using cell-attached, inside-out and outside-out configurations of the patch-clamp recording technique. Patches from the apical membrane typically contained many channels with unitary conductances ranging from 30 to 175 pS in symmetrical K+ solutions. Channel density was so high that unitary currents could be resolved only at negative voltages; at positive voltages patch recordings resembled whole-cell recordings. These multi-channel patches had a small but significant resting conductance that was strongly activated by depolarization. Patch current was highly K+ selective, with a PK/PNa ratio of 28. Patches containing single K+ channels were obtained by allowing the apical membrane to redistribute into the basolateral membrane with time. Two types of K+ channels were observed in isolation. Ca(2+)-dependent channels of large conductance (135-175 pS) were activated in cell-attached patches by strong depolarization, with a half-activation voltage of approximately -10 mV. An ATP-blocked K+ channel of 100 pS was activated in cell-attached patches by weak depolarization, with a half-activation voltage of approximately -47 mV. All apical K+ channels were blocked by the sour taste stimulus citric acid directly applied to outside-out and perfused cell-attached patches. The bitter stimulus quinine also blocked all channels when applied directly by altering channel gating to reduce the open probability. When quinine was applied extracellularly only to the membrane outside the patch pipette and also to inside-out patches, it produced a flickery block. Thus, sour and bitter taste stimuli appear to block the same apical K+ channels via different mechanisms to produce depolarizing receptor potentials.

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