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Article ; Online: Basolateral membrane K+ channels in renal epithelial cells.

Hamilton, Kirk L / Devor, Daniel C

American journal of physiology. Renal physiology

2012 Volume 302, Issue 9, Page(s) F1069–81

Abstract: ... the representative basolateral K(+) channels of the nephron. The basolateral K(+) channels of the renal epithelia are ... distributions) of membrane transport proteins in the apical and basolateral membranes of the cell. K(+) channels ... identified in the human genome. Epithelial K(+) channels can be located within either or both the apical and basolateral ...

Abstract	The major function of epithelial tissues is to maintain proper ion, solute, and water homeostasis. The tubule of the renal nephron has an amazingly simple structure, lined by epithelial cells, yet the segments (i.e., proximal tubule vs. collecting duct) of the nephron have unique transport functions. The functional differences are because epithelial cells are polarized and thus possess different patterns (distributions) of membrane transport proteins in the apical and basolateral membranes of the cell. K(+) channels play critical roles in normal physiology. Over 90 different genes for K(+) channels have been identified in the human genome. Epithelial K(+) channels can be located within either or both the apical and basolateral membranes of the cell. One of the primary functions of basolateral K(+) channels is to recycle K(+) across the basolateral membrane for proper function of the Na(+)-K(+)-ATPase, among other functions. Mutations of these channels can cause significant disease. The focus of this review is to provide an overview of the basolateral K(+) channels of the nephron, providing potential physiological functions and pathophysiology of these channels, where appropriate. We have taken a "K(+) channel gene family" approach in presenting the representative basolateral K(+) channels of the nephron. The basolateral K(+) channels of the renal epithelia are represented by members of the KCNK, KCNJ, KCNQ, KCNE, and SLO gene families.
MeSH term(s)	Cell Membrane/physiology ; Epithelial Cells/physiology ; Homeostasis/physiology ; Humans ; Kidney/cytology ; Kidney/physiology ; Potassium/metabolism ; Potassium Channels/genetics ; Potassium Channels/physiology ; Sodium-Potassium-Exchanging ATPase/physiology
Chemical Substances	Potassium Channels ; Sodium-Potassium-Exchanging ATPase (EC 7.2.2.13) ; Potassium (RWP5GA015D)
Language	English
Publishing date	2012-02-15
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't ; Review
ZDB-ID	603837-2
ISSN	1522-1466 ; 0363-6127
ISSN (online)	1522-1466
ISSN	0363-6127
DOI	10.1152/ajprenal.00646.2011
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Article: WNK4 regulates apical and basolateral Cl- flux in extrarenal epithelia.

Kahle, Kristopher T / Gimenez, Ignacio / Hassan, Hatim / Wilson, Frederick H / Wong, Robert D / Forbush, Biff / Aronson, Peter S / Lifton, Richard P

Proceedings of the National Academy of Sciences of the United States of America

2004 Volume 101, Issue 7, Page(s) 2064–2069

Abstract: ... NaCl cotransporter and the K(+) channel ROMK. We now demonstrate expression of WNK4 mRNA and protein ... variably associating with tight junctions, lateral membranes, and cytoplasm. Epithelia expressing WNK4 ... on the activity of mediators of epithelial Cl(-) flux whose extrarenal expression overlaps with WNK4. WNK4 proved ...

Abstract	Mutations in the serine-threonine kinase WNK4 [with no lysine (K) 4] cause pseudohypoaldosteronism type II, a Mendelian disease featuring hypertension with hyperkalemia. In the kidney, WNK4 regulates the balance between NaCl reabsorption and K(+) secretion via variable inhibition of the thiazide-sensistive NaCl cotransporter and the K(+) channel ROMK. We now demonstrate expression of WNK4 mRNA and protein outside the kidney. In extrarenal tissues, WNK4 is found almost exclusively in polarized epithelia, variably associating with tight junctions, lateral membranes, and cytoplasm. Epithelia expressing WNK4 include sweat ducts, colonic crypts, pancreatic ducts, bile ducts, and epididymis. WNK4 is also expressed in the specialized endothelium of the blood-brain barrier. These epithelia and endothelium all play important roles in Cl(-) transport. Because WNK4 is known to regulate renal Cl(-) handling, we tested WNK4's effect on the activity of mediators of epithelial Cl(-) flux whose extrarenal expression overlaps with WNK4. WNK4 proved to be a potent inhibitor of the activity of both the Na(+)-K(+)-2Cl(-) cotransporter (NKCC1) and the Cl(-)/base exchanger SLC26A6 (CFEX) (>95% inhibition of NKCC1-mediated (86)Rb influx, P < 0.001; >80% inhibition of CFEX-mediated [(14)C] formate uptake, P < 0.001), mediators of Cl(-) flux across basolateral and apical membranes, respectively. In contrast, WNK4 showed no inhibition of pendrin, a related Cl(-)/base exchanger. These findings indicate a general role for WNK4 in the regulation of electrolyte flux in diverse epithelia. Moreover, they reveal that WNK4 regulates the activities of a diverse group of structurally unrelated ion channels, cotransporters, and exchangers.
MeSH term(s)	Animals ; Blotting, Western ; Carrier Proteins/genetics ; Carrier Proteins/metabolism ; Cell Polarity ; Chlorides/metabolism ; Epithelium/metabolism ; Humans ; Immunohistochemistry ; Ion Transport ; Kidney/metabolism ; Membrane Proteins/genetics ; Membrane Proteins/metabolism ; Membrane Transport Proteins ; Mice ; Oocytes/metabolism ; Protein-Serine-Threonine Kinases/genetics ; Protein-Serine-Threonine Kinases/metabolism ; RNA, Messenger/genetics ; RNA, Messenger/metabolism ; Sodium-Potassium-Chloride Symporters/genetics ; Sodium-Potassium-Chloride Symporters/metabolism ; Solute Carrier Family 12, Member 2 ; Xenopus laevis
Chemical Substances	Carrier Proteins ; Chlorides ; Membrane Proteins ; Membrane Transport Proteins ; RNA, Messenger ; SLC12A2 protein, human ; SLC26A4 protein, human ; SLC26A6 protein, human ; Slc12a2 protein, mouse ; Sodium-Potassium-Chloride Symporters ; Solute Carrier Family 12, Member 2 ; Prkwnk4 protein, mouse (EC 2.7.1.-) ; Protein-Serine-Threonine Kinases (EC 2.7.11.1) ; WNK4 protein, human (EC 2.7.11.1)
Language	English
Publishing date	2004-02-17
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, P.H.S.
ZDB-ID	209104-5
ISSN	1091-6490 ; 0027-8424
ISSN (online)	1091-6490
ISSN	0027-8424
DOI	10.1073/pnas.0308434100
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Article ; Online: Caveolin-1 Deficiency Inhibits the Basolateral K+ Channels in the Distal Convoluted Tubule and Impairs Renal K+ and Mg2+ Transport.

Wang, Lijun / Zhang, Chengbiao / Su, Xiaotong / Lin, Dao-Hong / Wang, Wenhui

Journal of the American Society of Nephrology : JASN

2015 Volume 26, Issue 11, Page(s) 2678–2690

Abstract: Kcnj10 encodes the inwardly rectifying K(+) channel Kir4.1 in the basolateral membrane ... of epithelial Na(+) channel-α. Furthermore, the urinary excretion of Mg(2+) and K(+) was significantly higher ... channel are incompletely characterized. Here, patch-clamp experiments in Kcnj10-transfected HEK293 cells ...

Abstract	Kcnj10 encodes the inwardly rectifying K(+) channel Kir4.1 in the basolateral membrane of the distal convoluted tubule (DCT) and is activated by c-Src. However, the regulation and function of this K(+) channel are incompletely characterized. Here, patch-clamp experiments in Kcnj10-transfected HEK293 cells demonstrated that c-Src-induced stimulation of Kcnj10 requires coexpression of caveolin-1 (cav-1), and immunostaining showed expression of cav-1 in the basolateral membrane of parvalbumin-positive DCT. Patch-clamp experiments detected a 40-pS inwardly rectifying K(+) channel, a heterotetramer of Kir4.1/Kir5.1, in the basolateral membrane of the early DCT (DCT1) in both wild-type (WT) and cav-1-knockout (KO) mice. However, the activity of this basolateral 40-pS K(+) channel was lower in KO mice than in WT mice. Moreover, the K(+) reversal potential (an indication of membrane potential) was less negative in the DCT1 of KO mice than in the DCT1 of WT mice. Western blot analysis demonstrated that cav-1 deficiency decreased the expression of the Na(+)/Cl(-) cotransporter and Ste20-proline-alanine-rich kinase (SPAK) but increased the expression of epithelial Na(+) channel-α. Furthermore, the urinary excretion of Mg(2+) and K(+) was significantly higher in KO mice than in WT mice, and KO mice developed hypomagnesemia, hypocalcemia, and hypokalemia. We conclude that disruption of cav-1 decreases basolateral K(+) channel activity and depolarizes the cell membrane potential in the DCT1 at least in part by suppressing the stimulatory effect of c-Src on Kcnj10. Furthermore, the decrease in Kcnj10 and Na(+)/Cl(-) cotransporter expression induced by cav-1 deficiency may underlie the compromised renal transport of Mg(2+), Ca(2+), and K(+).
MeSH term(s)	Animals ; Calcium/metabolism ; Caveolin 1/genetics ; Caveolin 1/physiology ; Cell Membrane/metabolism ; Electrolytes ; Female ; Gitelman Syndrome/metabolism ; Green Fluorescent Proteins/metabolism ; HEK293 Cells ; Humans ; Hypokalemia/metabolism ; Kidney/metabolism ; Magnesium/metabolism ; Male ; Membrane Potentials ; Mice ; Mice, Inbred C57BL ; Mice, Knockout ; Microscopy, Fluorescence ; Patch-Clamp Techniques ; Potassium/metabolism ; Potassium Channels, Inwardly Rectifying/metabolism ; Transfection
Chemical Substances	CAV1 protein, human ; Cav1 protein, mouse ; Caveolin 1 ; Electrolytes ; Kcnj10 (channel) ; Potassium Channels, Inwardly Rectifying ; Green Fluorescent Proteins (147336-22-9) ; Magnesium (I38ZP9992A) ; Potassium (RWP5GA015D) ; Calcium (SY7Q814VUP)
Language	English
Publishing date	2015-11
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural
ZDB-ID	1085942-1
ISSN	1533-3450 ; 1046-6673
ISSN (online)	1533-3450
ISSN	1046-6673
DOI	10.1681/ASN.2014070658
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Article ; Online: Direct inhibition of basolateral Kir4.1/5.1 and Kir4.1 channels in the cortical collecting duct by dopamine.

Zaika, Oleg L / Mamenko, Mykola / Palygin, Oleg / Boukelmoune, Nabila / Staruschenko, Alexander / Pochynyuk, Oleh

American journal of physiology. Renal physiology

2013 Volume 305, Issue 9, Page(s) F1277–87

Abstract: ... channels in the distal renal tubule are critical for K(+) recycling and controlling basolateral ... 1 and Kir4.1 channels in CCD cells via stimulation of D2-like receptors and subsequently PKC ... dopamine receptors. PKC blockade abolished the inhibition of basolateral K(+) channels by dopamine. Importantly ...

Abstract	It is recognized that dopamine promotes natriuresis by inhibiting multiple transporting systems in the proximal tubule. In contrast, less is known about the molecular targets of dopamine actions on water-electrolyte transport in the cortical collecting duct (CCD). Epithelial cells in the CCD are exposed to dopamine, which is synthesized locally or secreted from sympathetic nerve endings. Basolateral K(+) channels in the distal renal tubule are critical for K(+) recycling and controlling basolateral membrane potential to establish the driving force for Na(+) reabsorption. Here, we demonstrate that Kir4.1 and Kir5.1 are highly expressed in the mouse kidney cortex and are localized to the basolateral membrane of the CCD. Using patch-clamp electrophysiology in freshly isolated CCDs, we detected highly abundant 40-pS and scarce 20-pS single channel conductances, most likely representing Kir4.1/5.1 and Kir4.1 channels, respectively. Dopamine reversibly decreased the open probability of both channels, with a relatively greater action on the Kir4.1/5.1 heterodimer. This effect was mediated by D2-like but not D1-like dopamine receptors. PKC blockade abolished the inhibition of basolateral K(+) channels by dopamine. Importantly, dopamine significantly decreased the amplitude of Kir4.1/5.1 and Kir4.1 unitary currents. Consistently, dopamine induced an acute depolarization of basolateral membrane potential, as directly monitored using current-clamp mode in isolated CCDs. Therefore, we demonstrate that dopamine inhibits basolateral Kir4.1/5.1 and Kir4.1 channels in CCD cells via stimulation of D2-like receptors and subsequently PKC. This leads to depolarization of the basolateral membrane and a decreased driving force for Na(+) reabsorption in the distal renal tubule.
MeSH term(s)	Animals ; Dopamine/metabolism ; Kidney Cortex/cytology ; Kidney Cortex/metabolism ; Kidney Tubules, Collecting/cytology ; Kidney Tubules, Collecting/metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Patch-Clamp Techniques ; Potassium Channels, Inwardly Rectifying/metabolism ; Protein Kinase C/metabolism ; Receptors, Dopamine D2/metabolism ; Signal Transduction ; Sodium/metabolism ; Kir5.1 Channel
Chemical Substances	Kcnj10 (channel) ; Potassium Channels, Inwardly Rectifying ; Receptors, Dopamine D2 ; Sodium (9NEZ333N27) ; Protein Kinase C (EC 2.7.11.13) ; Dopamine (VTD58H1Z2X)
Language	English
Publishing date	2013-08-28
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	603837-2
ISSN	1522-1466 ; 0363-6127
ISSN (online)	1522-1466
ISSN	0363-6127
DOI	10.1152/ajprenal.00363.2013
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Article ; Online: Insulin and IGF-1 activate Kir4.1/5.1 channels in cortical collecting duct principal cells to control basolateral membrane voltage.

Zaika, Oleg / Palygin, Oleg / Tomilin, Viktor / Mamenko, Mykola / Staruschenko, Alexander / Pochynyuk, Oleh

American journal of physiology. Renal physiology

2015 Volume 310, Issue 4, Page(s) F311–21

Abstract: Potassium Kir4.1/5.1 channels are abundantly expressed at the basolateral membrane of principal ... known about their actions on potassium channels localized at the basolateral membrane. In this study ... 1/5.1 at both single channel and cellular levels. We demonstrated that K(+)-selective conductance ...

Abstract	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.
MeSH term(s)	Animals ; Cell Membrane/drug effects ; Dose-Response Relationship, Drug ; Electrophysiological Phenomena/drug effects ; Hypoglycemic Agents/pharmacology ; Insulin/pharmacology ; Insulin-Like Growth Factor I/antagonists & inhibitors ; Insulin-Like Growth Factor I/pharmacology ; Kidney Tubules, Collecting/chemistry ; Kidney Tubules, Collecting/drug effects ; Kidney Tubules, Collecting/metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Patch-Clamp Techniques ; Phosphoinositide-3 Kinase Inhibitors ; Potassium Channel Blockers/pharmacology ; Potassium Channels, Inwardly Rectifying/agonists ; Potassium Channels, Inwardly Rectifying/metabolism ; Signal Transduction/drug effects ; Kir5.1 Channel
Chemical Substances	Hypoglycemic Agents ; Insulin ; Kcnj10 (channel) ; Phosphoinositide-3 Kinase Inhibitors ; Potassium Channel Blockers ; Potassium Channels, Inwardly Rectifying ; Insulin-Like Growth Factor I (67763-96-6)
Language	English
Publishing date	2015-12-02
Publishing country	United States
Document type	Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
ZDB-ID	603837-2
ISSN	1522-1466 ; 0363-6127
ISSN (online)	1522-1466
ISSN	0363-6127
DOI	10.1152/ajprenal.00436.2015
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Article: Upregulation of apical sodium-chloride cotransporter and basolateral chloride channels is responsible for the maintenance of salt-sensitive hypertension.

Capasso, Giovambattista / Rizzo, Maria / Garavaglia, Maria Lisa / Trepiccione, Francesco / Zacchia, Miriam / Mugione, Alessandra / Ferrari, Patrizia / Paulmichl, Markus / Lang, Florian / Loffing, Johannes / Carrel, Monique / Damiano, Sara / Wagner, Carsten A / Bianchi, Giuseppe / Meyer, Giuliano

American journal of physiology. Renal physiology

2008 Volume 295, Issue 2, Page(s) F556–67

Abstract: ... chloride channels (ClC-K) were studied by Western blot experiments on renal cortex and by patch-clamp studies ... showing increased NCC on the apical membrane of DCT cells of MHS animals, and by clearance experiments ... 001) of NCC in the cortex; 3) alpha- and beta-sodium channels [epithelial Na+ channel (ENaC ...

Abstract	We investigated which of the NaCl transporters are involved in the maintenance of salt-sensitive hypertension. Milan hypertensive (MHS) rats were studied 3 mo after birth. In MHS, compared with normotensive strain (MNS), mRNA abundance, quantified by competitive PCR on isolated tubules, was unchanged, both for Na+/H+ isoform 3 (NHE3) and Na+-K+-2Cl- (NKCC2), but higher (119%, n = 5, P < 0.005) for Na+-Cl- (NCC) in distal convoluted tubules (DCT). These results were confirmed by Western blots, which revealed: 1) unchanged NHE3 in the cortex and NKCC2 in the outer medulla; 2) a significant increase (52%, n = 6, P < 0.001) of NCC in the cortex; 3) alpha- and beta-sodium channels [epithelial Na+ channel (ENaC)] unaffected in renal cortex and slightly reduced in the outer medulla, while gamma-ENaC remained unchanged. Pendrin protein expression was unaffected. The role of NCC was reinforced by immunocytochemical studies showing increased NCC on the apical membrane of DCT cells of MHS animals, and by clearance experiments demonstrating a larger sensitivity (P < 0.001) to bendroflumethiazide in MHS rats. Kidney-specific chloride channels (ClC-K) were studied by Western blot experiments on renal cortex and by patch-clamp studies on primary culture of DCT dissected from MNS and MHS animals. Electrophysiological characteristics of ClC-K channels were unchanged in MHS rats, but the number of active channels in a patch was 0.60 +/- 0.21 (n = 35) in MNS rats and 2.17 +/- 0.59 (n = 23) in MHS rats (P < 0.05). The data indicate that, in salt-sensitive hypertension, there is a strong upregulation, both of NCC and ClC-K along the DCT, which explains the persistence of hypertension.
MeSH term(s)	Aldosterone/metabolism ; Animals ; Chloride Channels/genetics ; Chloride Channels/metabolism ; Chloride-Bicarbonate Antiporters/metabolism ; Disease Models, Animal ; Epithelial Sodium Channels/metabolism ; Hypertension/genetics ; Hypertension/metabolism ; Hypertension/physiopathology ; Kidney Cortex/metabolism ; Kidney Cortex/physiopathology ; Kidney Medulla/metabolism ; Kidney Medulla/physiopathology ; Patch-Clamp Techniques ; RNA, Messenger/metabolism ; Rats ; Rats, Inbred Strains ; Sodium Chloride Symporters/genetics ; Sodium Chloride Symporters/metabolism ; Sodium Chloride, Dietary/adverse effects ; Sodium-Hydrogen Exchanger 3 ; Sodium-Hydrogen Exchangers/metabolism ; Sodium-Potassium-Chloride Symporters/metabolism ; Solute Carrier Family 12, Member 1 ; Sulfate Transporters ; Up-Regulation
Chemical Substances	Chloride Channels ; Chloride-Bicarbonate Antiporters ; Clcnka protein, rat ; Epithelial Sodium Channels ; RNA, Messenger ; Slc12a1 protein, rat ; Slc26A4 protein, rat ; Slc9a3 protein, rat ; Sodium Chloride Symporters ; Sodium Chloride, Dietary ; Sodium-Hydrogen Exchanger 3 ; Sodium-Hydrogen Exchangers ; Sodium-Potassium-Chloride Symporters ; Solute Carrier Family 12, Member 1 ; Sulfate Transporters ; Aldosterone (4964P6T9RB)
Language	English
Publishing date	2008-05-14
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	603837-2
ISSN	1522-1466 ; 1931-857X ; 0363-6127
ISSN (online)	1522-1466
ISSN	1931-857X ; 0363-6127
DOI	10.1152/ajprenal.00340.2007
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Article: Apical and basolateral conductance in cultured A6 cells.

Granitzer, M / Leal, T / Nagel, W / Crabbe, J

Pflugers Archiv : European journal of physiology

1991 Volume 417, Issue 5, Page(s) 463–468

Abstract: ... of the control values after blocking the K+ channels with Ba2+. The nature of the remaining conductance is presently ... membrane represents the major resistive barrier. Transcellular, apical and basolateral membrane ... at the basolateral membrane of 0.72 can be calculated. This value corresponds with the decrease in gi to about 25 ...

Abstract	Confluent monolayers of the cultured renal distal tubule cell line (A6) were impaled with microelectrodes under short-circuit conditions. Specific membrane conductances were calculated from equivalent circuit equations. Transport properties of the apical and basolateral membranes were investigated during control conditions and short-term increases in basolateral potassium concentration [K+] from 2.5 to 20 mmol/l, with or without 0.5 mmol/l Ba2+ at the basolateral side. As in most other epithelia, the apical membrane represents the major resistive barrier. Transcellular, apical and basolateral membrane conductances (gc, go and gi respectively), obtained from 22 acceptable microelectrode studies, averaged 61, 80 and 292 microS/cm2, respectively. There was a highly significant correlation between short-circuit current (Isc) and go, whereas gi was unrelated to Isc. The Isc, which averaged 4.1 microA/cm2, was almost completely blocked by amiloride. This was associated with fast hyperpolarization; the intracellular potential (Vsc) increased from -69 to -83 mV and the fractional apical resistance rose to nearly 100%. Using the values of Vsc during amiloride at normal and high [K+], an apparent transference number for K+ at the basolateral membrane of 0.72 can be calculated. This value corresponds with the decrease in gi to about 25% of the control values after blocking the K+ channels with Ba2+. The nature of the remaining conductance is presently unclear. The cellular current decreased during high [K+] and Ba2+, in part resulting from reduction of the electrochemical gradient for apical Na+ uptake due to the depolarization.(ABSTRACT TRUNCATED AT 250 WORDS)
MeSH term(s)	Animals ; Barium/pharmacology ; Biological Transport ; Cell Line ; Electric Conductivity ; Kidney Tubules, Distal/physiology ; Membrane Potentials/physiology ; Microelectrodes ; Potassium/metabolism ; Xenopus laevis
Chemical Substances	Barium (24GP945V5T) ; Potassium (RWP5GA015D)
Language	English
Publishing date	1991-01
Publishing country	Germany
Document type	Journal Article ; Research Support, Non-U.S. Gov't
ZDB-ID	6380-0
ISSN	1432-2013 ; 0031-6768
ISSN (online)	1432-2013
ISSN	0031-6768
DOI	10.1007/bf00370940
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Article: Activity of the basolateral K+ channels is coupled to the Na+-K+-ATPase in the cortical collecting duct.

Muto, Shigeaki / Asano, Yasushi / Wang, WenHui / Seldin, Donald / Giebisch, Gerhard

American journal of physiology. Renal physiology

2003 Volume 285, Issue 5, Page(s) F945–54

Abstract: ... Physiol Renal Physiol 276: F143-F158, 1999) on the transepithelial (VT) and basolateral membrane (VB ... dependent inhibition of K+ channels. ... voltages and basolateral K+ channel activity. Increasing bath K+ from 2.5 to 8.5 mM resulted in an initial ...

Abstract	Microelectrode and patch-clamp techniques were used in the isolated cortical collecting duct to study the effects of stimulating Na+-K+-ATPase by raising bath K+ (Fujii Y and Katz AI. Am J Physiol Renal Fluid Electrolyte Physiol 257: F595-F601, 1989 and Muto S, Asano Y, Seldin D, and Giebisch. Am J Physiol Renal Physiol 276: F143-F158, 1999) on the transepithelial (VT) and basolateral membrane (VB) voltages and basolateral K+ channel activity. Increasing bath K+ from 2.5 to 8.5 mM resulted in an initial hyperpolarization of both VT and VB followed by a delayed depolarization. The effects of raising bath K+ on VT and VB were attenuated by decreasing luminal Na+ from 146.8 to 14.0 mM and were abolished by removal of luminal Na+, whereas those were magnified in desoxycorticosterone acetate (DOCA)-treated rabbits. Increasing bath K+ also led to a significant reduction of the intracellular Na+ and Ca2+ concentrations. The transepithelial conductance (GT) or fractional apical membrane resistance (fRA) were unaltered during the initial hyperpolarization phase, whereas, in the late depolarization phase, there were an increase in GT and a decrease in fRA, both of which were attenuated in the presence of low luminal Na+ (14.0 mM). In tubules from DOCA-treated animals, bath Ba2+ not only caused a significantly larger initial hyperpolarization of VT and VB but also blunted the late depolarization by high bath K+. Nomega-nitro-l-arginine methyl ester (l-NAME) partially mimicked the effect of Ba2+ and decreased the amplitude of the late depolarization. Patch-clamp experiments showed that raising bath K+ from 2.5 to 8.5 mM resulted in an increased activity of the basolateral K+ channel, which was absent in the presence of l-NAME. We conclude that stimulation of Na+-K+-ATPase increases the basolateral K+ conductance and that this effect involves suppression of nitric oxide-dependent inhibition of K+ channels.
MeSH term(s)	Animals ; Barium/pharmacology ; Cell Membrane/physiology ; Desoxycorticosterone/pharmacology ; Electric Conductivity ; Electric Impedance ; Enzyme Inhibitors/pharmacology ; Epithelium/metabolism ; Epithelium/physiology ; Female ; In Vitro Techniques ; Intracellular Membranes/metabolism ; Intracellular Membranes/physiology ; Kidney Cortex ; Kidney Tubules, Collecting/drug effects ; Kidney Tubules, Collecting/metabolism ; Microelectrodes ; NG-Nitroarginine Methyl Ester/pharmacology ; Patch-Clamp Techniques ; Potassium/pharmacology ; Potassium Channels/metabolism ; Potassium Channels/physiology ; Rabbits ; Sodium-Potassium-Exchanging ATPase/metabolism
Chemical Substances	Enzyme Inhibitors ; Potassium Channels ; Barium (24GP945V5T) ; Desoxycorticosterone (40GP35YQ49) ; Sodium-Potassium-Exchanging ATPase (EC 3.6.3.9) ; Potassium (RWP5GA015D) ; NG-Nitroarginine Methyl Ester (V55S2QJN2X)
Language	English
Publishing date	2003-11
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, P.H.S.
ZDB-ID	603837-2
ISSN	1522-1466 ; 1931-857X ; 0363-6127
ISSN (online)	1522-1466
ISSN	1931-857X ; 0363-6127
DOI	10.1152/ajprenal.00081.2003
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Article: Effect of altered Na+ entry on expression of apical and basolateral transport proteins in A6 epithelia.

Lebowitz, Jonathan / An, Bing / Edinger, Robert S / Zeidel, Mark L / Johnson, John P

American journal of physiology. Renal physiology

2003 Volume 285, Issue 3, Page(s) F524–31

Abstract: ... into epithelial cells alter the ability of these cells to reabsorb Na+. We previously modeled this load dependence ... associated with alterations in either the whole cell content or apical membrane distribution ... of sodium channel (ENaC) subunits or on basolateral expression of either of the subunits of the Na+-K+-ATPase ...

Abstract	In several in vivo settings, prolonged alterations in the rate of apical Na+ entry into epithelial cells alter the ability of these cells to reabsorb Na+. We previously modeled this load dependence of transport in A6 cells by either decreasing Na+ entry via apical Na+ removal or amiloride or enhancing Na+ entry by chronic short-circuiting (Rokaw MD, Sarac E, Lechman E, West M, Angeski J, Johnson JP, and Zeidel ML. Am J Physiol Cell Physiol 270: C600-C607, 1996). Inhibition of Na+ entry by either method was associated with striking downregulation of transport rate as measured by short-circuit current (Isc), which recovered to basal levels of transport over a period of hours. Conversely, upregulation of Na+ entry by short-circuiting resulted in a sustained increase in transport rate that also returned to basal levels over a period of hours. The current studies were undertaken to determine whether these conditions were associated with alterations in either the whole cell content or apical membrane distribution of sodium channel (ENaC) subunits or on basolateral expression of either of the subunits of the Na+-K+-ATPase. We compared these effects to those achieved by chronic upregulation of Na+ transport by aldosterone. Whole cell levels of ENaC subunits were measured by immunoblot following 18-h inhibition of Na+ entry achieved by either tetramethylammonium replacement of Na+ or apical amiloride or after an 18-h increase in Na+ entry achieved by chronic short-circuiting. None of these maneuvers significantly altered the whole cell content of any of the ENaC subunits compared with control cells. We then examined the effects of these maneuvers on apical membrane ENaC expression using domain-specific biotinylation and immunoblot. Inhibition of Na+ entry by either method was associated with a profound decrease in apical membrane beta-ENaC without significant changes in apical membrane alpha-or gamma-ENaC amounts. Restoration of apical Na+ and/or removal of amiloride resulted in return of Isc to control levels over 2 h and coincided with return of apical beta-ENaC to control levels without change in apical alpha- or gamma-ENaC. Stimulation of Na+ transport by short-circuiting, in contrast, did not significantly alter apical membrane composition of any of the ENaC subunits. Basolateral expression of Na+-K+-ATPase was also measured by biotinylation and immunoblot and was unchanged under all conditions. Aldosterone increased basolateral expression of the alpha-subunit of Na+-K+-ATPase. These results suggest that chronic downregulation of transport is mediated, in part, by a selective decrease in apical membrane ENaC expression, consistent with our previous observations of noncoordinate regulation of ENaC expression under varying transport conditions in A6 cells. The chronic increase in the rate of Na+ entry is not associated with any of the changes in transporter density at either apical or basolateral membrane seen with aldosterone, suggesting that these two mechanisms of augmenting transport are completely distinct.
MeSH term(s)	Aldosterone/pharmacology ; Amiloride/pharmacology ; Animals ; Cell Line ; Cell Membrane/drug effects ; Cell Membrane/metabolism ; Cell Polarity ; Epithelial Cells/drug effects ; Epithelial Cells/metabolism ; Gene Expression Regulation ; Ion Transport/drug effects ; Sodium/metabolism ; Sodium Channels/metabolism ; Sodium-Potassium-Exchanging ATPase/metabolism
Chemical Substances	Sodium Channels ; Aldosterone (4964P6T9RB) ; Amiloride (7DZO8EB0Z3) ; Sodium (9NEZ333N27) ; Sodium-Potassium-Exchanging ATPase (EC 3.6.3.9)
Language	English
Publishing date	2003-09
Publishing country	United States
Document type	Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, P.H.S.
ZDB-ID	603837-2
ISSN	1522-1466 ; 1931-857X ; 0363-6127
ISSN (online)	1522-1466
ISSN	1931-857X ; 0363-6127
DOI	10.1152/ajprenal.00366.2001
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Article: Regulation of renal proximal tubule basolateral potassium channels.

Sackin, H

Progress in clinical and biological research

1990 Volume 334, Page(s) 231–249

Abstract: ... in metabolic activity leading to membrane depolarization would reduce the open-probability of the basolateral K channel ... of basolateral K channels may explain both electrolyte and volume homeostasis in the amphibian proximal tubule ... from stretch-activated K channels. This same stretch-activation property may also be involved in the VRD that occurs ...

Abstract	In summary, these studies report a voltage-gated, stretch-activated K channel at the basolateral membrane of amphibian proximal tubule. In the normal range of potential, any reduction in metabolic activity leading to membrane depolarization would reduce the open-probability of the basolateral K channel, thereby preventing excessive loss of K out of the cell. This type of voltage gating is consistent with the decrease in macroscopic K conductance observed in perfused frog tubules after cell depolarization (Messner et al., 1985). However, it does not account for the delayed increase in basolateral K conductance that accompanies Na-substrate cotransport across the apical membrane. The stretch-activation property of basolateral K channels may explain both electrolyte and volume homeostasis in the amphibian proximal tubule. Na-substrate cotransport produces a gradual increase in cell volume in several preparations (Hempling and Hare 1961; Hacking and Eddy 1981; Hudson and Schultz 1988;). Hence, the observed increase in K conductance during luminal addition of Na-cotransported substrates may be mediated by small changes in cell volume. For example, a stretch-activated K channel, stimulated by a 1% increase in cell volume, would allow K to exit the cell down its electrochemical gradient, thereby balancing the increased K uptake associated with greater Na pump activity. A number of studies have provided evidence that cell swelling increases macroscopic K conductance (Davis and Finn 1982; Germann et al. 1986; Grinstein et al. 1982; Grinstein et al. 1984; Hamill 1983; Hoffmann 1985; Lau et al. 1984; Lopes and Guggino 1987; Richards and Dawson 1986) as well as chloride channel activity (Hudson and Schultz 1988). However, the present study is the first to suggest that the swelling-induced increase in basolateral K conductance results from stretch-activated K channels. This same stretch-activation property may also be involved in the VRD that occurs during exposure of proximal tubule cells to hypotonic media (Dellesaga and Grantham 1973; Welling et al. 1985; Lopes and Guggino 1987; Kirk et al 1987). Since cell swelling undoubtably increases membrane tension (Kelly and Macklem 1988), swollen amphibian proximal tubule cells would lose K because of an increase in the open probability of stretch-activated K channels. The additional exit of bicarbonate and water would restore the cells to their original volume.
MeSH term(s)	Animals ; Epithelial Cells ; Epithelium/physiology ; Ion Channel Gating ; Kidney Tubules, Proximal/physiology ; Necturus/physiology ; Potassium Channels/physiology
Chemical Substances	Potassium Channels
Language	English
Publishing date	1990
Publishing country	United States
Document type	Journal Article ; Research Support, U.S. Gov't, P.H.S. ; Review
ISSN	0361-7742
ISSN	0361-7742
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