Small and maxi K+ channels in the basolateral membrane of isolated crypts from rat distal colon: single-channel and slow whole-cell recordings

1992 ◽  
Vol 420 (1) ◽  
pp. 54-60 ◽  
Author(s):  
Birgitta-Christina Burckhardt ◽  
Heinz G�gelein
Keyword(s):  
Single Channel ◽  
Basolateral Membrane ◽  
Distal Colon ◽  
Whole Cell ◽  
K Channels ◽  
Rat Distal Colon ◽  
Whole Cell Recordings

Substrate activation of mechanosensitive, whole cell currents in renal proximal tubule

1993 ◽  
Vol 264 (4) ◽  
pp. F697-F714 ◽  
Author(s):  
D. Cemerikic ◽  
H. Sackin
Keyword(s):  
Proximal Tubule ◽  
Cell Volume ◽  
Single Channel ◽  
Basolateral Membrane ◽  
Bulk Composition ◽  
Physiological Role ◽  
Bathing Solution ◽  
Pipette Solution ◽  
Whole Cell ◽  
K Channels

Isolated, polarized, proximal tubule cells of Rana pipiens were voltage clamped and examined for both single-channel and whole cell currents. Barium-sensitive whole cell conductances were calculated from the difference in slopes of the current-voltage relations before and after 5 mM external barium. In 11 voltage-clamped cells with high K in the pipette (and cell), isosmotic addition of 40 mM glucose to the bathing solution increased cell volume by 23 +/- 4% within 2-3 min and increased barium-sensitive conductance by 40 +/- 10% from 0.5 to 0.7 nS (P < 0.005, with each cell as its own control). Isosmotic addition of nonmetabolizable methyl-alpha-D-glucopyranoside, which enters with Na across the apical membrane, produced a similar increase in barium-sensitive conductance (30 +/- 13%). In contrast, 3-O-methyl-D-glucopyranose, which is not cotransported with Na, did not alter either cell volume or barium-sensitive conductance. Isosmotic addition of 40 mM phenylalanine (Phe) increased cell volume by 21 +/- 3% and increased barium-sensitive conductance by 36 +/- 19% from 1.1 to 1.5 nS (P < 0.005, with each cell as its own control; n = 8). All K channels observed at the basolateral membrane of these amphibian cells were found to be activated by pipette suction (stretch) and inhibited by 5 mM external barium (outside-out patches). Hence, stretch-activated (SA) K channels must be mediating the macroscopic increase in whole cell K conductance (GK) after isosmotic addition of glucose and Phe. The process does not seem to involve changes in ATP, because Phe increased GK even more when cytosolic ATP was maintained at high levels (10(-4) M extracellular ouabain and 5 mM intracellular ATP). It is also unlikely that changes in cell pH or calcium mediate the increase in GK, because the bulk composition of the cell is "clamped" by the pipette solution in these experiments (1-micron tip patch pipettes). Consequently, the substrate-induced increase in GK probably arises from a swelling-associated deformation of the submembane cytoskeleton or a direct change in membrane tension. In either case, SA channels would play a physiological role in proximal tubule K homeostasis during sugar and amino acid reabsorption in the proximal tubule of the kidney.

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).

scholarly journals Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage

2016 ◽  
Vol 310 (4) ◽  
pp. F311-F321 ◽  
Author(s):  
Oleg Zaika ◽  
Oleg Palygin ◽  
Viktor Tomilin ◽  
Mykola Mamenko ◽  
Alexander Staruschenko ◽  
...  
Keyword(s):  
Single Channel ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Sodium Reabsorption ◽  
Cortical Collecting Duct ◽  
Open Probability ◽  
Whole Cell ◽  
Principal Cells ◽  
Basolateral Side ◽  
Kinase Cascade

Potassium Kir4.1/5.1 channels are abundantly expressed at the basolateral membrane of principal cells in the cortical collecting duct (CCD), where they are thought to modulate transport rates by controlling transepithelial voltage. Insulin and insulin-like growth factor-1 (IGF-1) stimulate apically localized epithelial sodium channels (ENaC) to augment sodium reabsorption in the CCD. However, little is known about their actions on potassium channels localized at the basolateral membrane. In this study, we implemented patch-clamp analysis in freshly isolated murine CCD to assess the effect of these hormones on Kir4.1/5.1 at both single channel and cellular levels. We demonstrated that K+-selective conductance via Kir4.1/5.1 is the major contributor to the macroscopic current recorded from the basolateral side in principal cells. Acute treatment with 10 μM amiloride (ENaC blocker), 100 nM tertiapin-Q (TPNQ; ROMK inhibitor), and 100 μM ouabain (Na+-K+-ATPase blocker) failed to produce a measurable effect on the macroscopic current. In contrast, Kir4.1 inhibitor nortriptyline (100 μM), but not fluoxetine (100 μM), virtually abolished whole cell K+-selective conductance. Insulin (100 nM) markedly increased the open probability of Kir4.1/5.1 and nortriptyline-sensitive whole cell current, leading to significant hyperpolarization of the basolateral membrane. Inhibition of the phosphatidylinositol 3-kinase cascade with LY294002 (20 μM) abolished action of insulin on Kir4.1/5.1. IGF-1 had similar stimulatory actions on Kir4.1/5.1-mediated conductance only when applied at a higher (500 nM) concentration and was ineffective at 100 nM. We concluded that both insulin and, to a lesser extent, IGF-1 activate Kir4.1/5.1 channel activity and open probability to hyperpolarize the basolateral membrane, thereby facilitating Na+ reabsorption in the CCD.

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.

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.

Bicarbonate-stimulated [14C]butyrate uptake in basolateral membrane vesicles of rat distal colon

1993 ◽  
Vol 105 (3) ◽  
pp. 725-732 ◽  
Author(s):  
Diedre A. Reynolds ◽  
Vazhaikkurichi M. Rajendran ◽  
Henry J. Binder
Keyword(s):  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Distal Colon ◽  
Basolateral Membrane Vesicles ◽  
Rat Distal Colon

scholarly journals Basolateral K channels in an insect epithelium. Channel density, conductance, and block by barium.

1986 ◽  
Vol 87 (3) ◽  
pp. 443-466 ◽  
Author(s):  
J W Hanrahan ◽  
N K Wills ◽  
J E Phillips ◽  
S A Lewis
Keyword(s):  
Single Channel ◽  
Short Circuit ◽  
Noise Analysis ◽  
Basolateral Membrane ◽  
Membrane Conductance ◽  
Short Circuit Current ◽  
Corner Frequency ◽  
Fluctuation Analysis ◽  
K Channels ◽  
K Current

K channels in the basolateral membrane of insect hindgut were studied using current fluctuation analysis and microelectrodes. Locust recta were mounted in Ussing-type chambers containing Cl-free saline and cyclic AMP (cAMP). A transepithelial K current was induced by raising serosal [K] under short-circuit conditions. Adding Ba to the mucosal (luminal) side under these conditions had no effect; however, serosal Ba reversibly inhibited the short-circuit current (Isc), increased transepithelial resistance (Rt), and added a Lorentzian component to power density spectra of the Isc. A nonlinear relationship between corner frequency and serosal [Ba] was observed, which suggests that the rate constant for Ba association with basolateral channels increased as [Ba] was elevated. Microelectrode experiments revealed that the basolateral membrane hyperpolarized when Ba was added: this change in membrane potential could explain the nonlinearity of the 2 pi fc vs. [Ba] relationship if external Ba sensed about three-quarters of the basolateral membrane field. Conventional microelectrodes were used to determine the correspondence between transepithelially measured current noise and basolateral membrane conductance fluctuations, and ion-sensitive microelectrodes were used to measure intracellular K activity (acK). From the relationship between the net electrochemical potential for K across the basolateral membrane and the single channel current calculated from noise analysis, we estimate that the conductance of basolateral K channels is approximately 60 pS, and that there are approximately 180 million channels per square centimeter of tissue area.

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