Developmental Expression of Na and K Channel Proteins in the Rat Renal Cortical Collecting Duct (CCD) † 1851

We have employed the patch-clamp technique to investigate the role of the actin cytoskeleton in the modulation of the low-conductance K+ channel in the apical membrane of the rat cortical collecting duct (CCD). This K+ channel is inactivated by application of cytochalasin B or D, both compounds known to disrupt actin filaments. The effect of both cytochalasins, B and D, was fully reversible in cell-attached patches, but channel activity could not be fully restored in excised membrane patches. The effect of cytochalasins on channel activity was specific and resulted from depolymerization of the actin cytoskeleton, since application of 10 microM chaetoglobosin C, a cytochalasin analogue that does not depolymerize the actin filaments, had no effect on channel activity in inside-out patches. Addition of either actin monomers or of the polymerizing actin filaments in inside-out patches to the cytosolic medium had no effect on channel activity. This suggests that cytochalasin B- or D-induced inactivation of apical K+ channels is not caused by obstruction of the channel pore by actin. We also observed that channel inhibition by cytochalasin B or D could be blocked by pretreatment with 5 microM phalloidin, a compound that stabilizes actin filaments. We conclude that apical K+ channel activity depends critically on the integrity of the actin cytoskeleton.

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Stimulation of total CO2 flux by 10% CO2 in rabbit CCD: role of an apical Sch-28080- and Ba-sensitive mechanism

AJP Renal Physiology ◽

10.1152/ajprenal.1994.267.1.f114 ◽

1994 ◽

Vol 267 (1) ◽

pp. F114-F120 ◽

Cited By ~ 14

Author(s):

X. Zhou ◽

C. S. Wingo

Keyword(s):

Collecting Duct ◽

Co2 Flux ◽

K Channel ◽

Co2 Absorption ◽

Cortical Collecting Duct ◽

Atpase Inhibitor ◽

Contrast Exposure ◽

Stimulation Of

These studies examine the effect of ambient PCO2 on net bicarbonate (total CO2) absorption by the in vitro perfused cortical collecting duct (CCD) from K-replete rabbits and the mechanism responsible for this effect. Exposure to 10% CO2 increased net bicarbonate flux (total CO2 flux, JtCO2) by 1.8-fold (P < 0.005), and this effect was inhibited by luminal 10 microM Sch-28080, an H-K-adenosinetriphosphatase (H-K-ATPase) inhibitor. In contrast, exposure to 10% CO2 significantly decreased Rb efflux, and this decrement in Rb efflux was blocked by luminal 2 mM Ba, a K channel blocker. Thus transepithelial tracer Rb flux did not increase upon exposure to 10% CO2 as we have observed in this segment under K-restricted conditions. The observation that 10% CO2 increased net bicarbonate absorption without a change in absorptive Rb flux suggested that 10% CO2 increased apical K recycling. To test this hypothesis, we examined whether luminal Ba inhibited the stimulation of luminal acidification induced by 10% CO2. If apical K exit were necessary for full activation of proton secretion, then inhibiting K exit should indirectly affect the stimulation of JtCO2 by 10% CO2. In fact, the effect of 10% CO2 on JtCO2 in the presence of 2 mM luminal Ba was quantitatively indistinguishable from the effect of 10% CO2 on JtCO2 in the presence of 10 microM luminal Sch-28080.(ABSTRACT TRUNCATED AT 250 WORDS)

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Arachidonic acid inhibits activity of cloned renal K+ channel, ROMK1

AJP Renal Physiology ◽

10.1152/ajprenal.1996.271.3.f588 ◽

1996 ◽

Vol 271 (3) ◽

pp. F588-F594 ◽

Cited By ~ 12

Author(s):

C. M. Macica ◽

Y. Yang ◽

S. C. Hebert ◽

W. H. Wang

Keyword(s):

Arachidonic Acid ◽

Membrane Fluidity ◽

Collecting Duct ◽

K Channel ◽

Thick Ascending Limb ◽

Cortical Collecting Duct ◽

Channel Activity ◽

Lipoxygenase Inhibitor ◽

Open Probability ◽

Apical Membranes

Arachidonic acid (AA) has been shown to inhibit the activity of the low-conductance ATP-sensitive K+ channel in the apical membrane of the cortical collecting duct [W. Wang, A. Cassola, and G. Giebisch. Am. J. Physiol. 262 (Renal Fluid Electrolyte Physiol. 31): F554-F559, 1992]. ROMK1, a K+ channel derived from the rat renal outer medulla, shares many biophysical properties of the native low-conductance K+ channel, which is localized to the apical membranes of the cortical collecting duct and thick ascending limb. This study was designed to determine whether the ROMK channel maintains the property of AA sensitivity of the native low-conductance K+ channel. Experiments were conducted in Xenopus oocytes injected with cRNA encoding the ROMK1 channel by use of patch-clamp techniques. We have confirmed previous reports that the cloned ROMK1 has similar channel kinetics, high open probability, and inward slope conductance as the native low-conductance K+ channel, respectively. Addition of 5 microM AA to an inside-out patch resulted in reversible inhibition of channel activity at a concentration similar to the inhibitor constant for AA on the native K+ channel. The effect of AA on channel activity was preserved in the presence of 10 microM indomethacin, a cyclooxygenase inhibitor, 4 microM cinnamyl-3,4-dihydroxycyanocinnamate, a lipoxygenase inhibitor, and 4 microM 17-octadecynoic acid, an inhibitor of cytochrome P-450 monooxygenases, thus indicating that the effect of AA was not mediated by metabolites of AA. The effect did not appear to be the result of changes in membrane fluidity, since 5 microM eicosatetraynoic acid, an AA analogue that is a potent modulator of membrane fluidity, had no effect. Furthermore, the addition of AA to the outside of the patch also had no effect on channel activity. These results indicate that, like the native low-conductance channel, AA is able to directly inhibit ROMK1 channel activity.

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Arachidonic acid inhibits basolateral K channels in the cortical collecting duct via cytochrome P-450 epoxygenase-dependent metabolic pathways

AJP Renal Physiology ◽

10.1152/ajprenal.00038.2008 ◽

2008 ◽

Vol 294 (6) ◽

pp. F1441-F1447 ◽

Cited By ~ 10

Author(s):

ZhiJian Wang ◽

Yuan Wei ◽

John R. Falck ◽

Krishnam Raju Atcha ◽

Wen-Hui Wang

Keyword(s):

Arachidonic Acid ◽

Collecting Duct ◽

Rat Kidney ◽

Inhibitory Effect ◽

K Channel ◽

Dependent Manner ◽

Cortical Collecting Duct ◽

Patch Clamp Technique ◽

K Channels ◽

Cytochrome P 450

We used the patch-clamp technique to study the effect of arachidonic acid (AA) on basolateral 18-pS K channels in the principal cell of the cortical collecting duct (CCD) of the rat kidney. Application of AA inhibited the 18-pS K channels in a dose-dependent manner and 10 μM AA caused a maximal inhibition. The effect of AA on the 18-pS K channel was specific because application of 11,14,17-eicosatrienoic acid had no effect on channel activity. Also, the inhibitory effect of AA on the 18-pS K channels was abolished by blocking cytochrome P-450 (CYP) epoxygenase with N-methylsulfonyl-6-(propargyloxyphenyl)hexanamide (MS-PPOH) but was not affected by inhibiting CYP ω-hydroxylase or cyclooxygenase. The notion that the inhibitory effect of AA was mediated by CYP epoxygenase-dependent metabolites was further supported by the observation that application of 100 nM 11,12-epoxyeicosatrienoic acid (EET) mimicked the effect of AA and inhibited the basolateral 18-pS K channels. In contrast, addition of either 5,6-, 8,9-, or 14,15-EET failed to inhibit the 18-pS K channels. Moreover, application of 11,12-EET was still able to inhibit the 18-pS K channels in the presence of MS-PPOH. This suggests that 11,12-EET is a mediator for the AA-induced inhibition of the 18-pS K channels. We conclude that AA inhibits basolateral 18-pS K channels by a CYP epoxygenase-dependent pathway and that 11,12-EET is a mediator for the effect of AA on basolateral K channels in the CCD.

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Angiotensin II type 2 receptor regulates ROMK-like K+ channel activity in the renal cortical collecting duct during high dietary K+ adaptation

AJP Renal Physiology ◽

10.1152/ajprenal.00141.2014 ◽

2014 ◽

Vol 307 (7) ◽

pp. F833-F843 ◽

Cited By ~ 13

Author(s):

Yuan Wei ◽

Yi Liao ◽

Beth Zavilowitz ◽

Jin Ren ◽

Wen Liu ◽

...

Keyword(s):

Collecting Duct ◽

No Synthase ◽

K Channel ◽

Ang Ii ◽

Cortical Collecting Duct ◽

Channel Activity ◽

High K ◽

Pka Pathway

The kidney adjusts K+ excretion to match intake in part by regulation of the activity of apical K+ secretory channels, including renal outer medullary K+ (ROMK)-like K+ channels, in the cortical collecting duct (CCD). ANG II inhibits ROMK channels via the ANG II type 1 receptor (AT1R) during dietary K+ restriction. Because AT1Rs and ANG II type 2 receptors (AT2Rs) generally function in an antagonistic manner, we sought to characterize the regulation of ROMK channels by the AT2R. Patch-clamp experiments revealed that ANG II increased ROMK channel activity in CCDs isolated from high-K+ (HK)-fed but not normal K+ (NK)-fed rats. This response was blocked by PD-123319, an AT2R antagonist, but not by losartan, an AT1R antagonist, and was mimicked by the AT2R agonist CGP-42112. Nitric oxide (NO) synthase is present in CCD cells that express ROMK channels. Blockade of NO synthase with N-nitro-l-arginine methyl ester and free NO with 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide potassium salt completely abolished ANG II-stimulated ROMK channel activity. NO enhances the synthesis of cGMP, which inhibits phosphodiesterases (PDEs) that normally degrade cAMP; cAMP increases ROMK channel activity. Pretreatment of CCDs with IBMX, a broad-spectrum PDE inhibitor, or cilostamide, a PDE3 inhibitor, abolished the stimulatory effect of ANG II on ROMK channels. Furthermore, PKA inhibitor peptide, but not an activator of the exchange protein directly activated by cAMP (Epac), also prevented the stimulatory effect of ANG II. We conclude that ANG II acts at the AT2R to stimulate ROMK channel activity in CCDs from HK-fed rats, a response opposite to that mediated by the AT1R in dietary K+-restricted animals, via a NO/cGMP pathway linked to a cAMP-PKA pathway.

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Expression and function of the Ca2+‐dependent SK3 K+ channel in mouse cortical collecting duct: Regulation by TRPV4

The FASEB Journal ◽

10.1096/fasebj.27.1_supplement.912.14 ◽

2013 ◽

Vol 27 (S1) ◽

Author(s):

Jonathan Berrout ◽

Mykola Mamenko ◽

Oleg L Zaika ◽

Oleh Pochynyuk ◽

Roger G O'Neil

Keyword(s):

Collecting Duct ◽

K Channel ◽

Cortical Collecting Duct ◽

And Function

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Activation of H+-K+-ATPase by CO2 requires a basolateral Ba2+-sensitive pathway during K restriction

AJP Renal Physiology ◽

10.1152/ajprenal.2000.279.1.f153 ◽

2000 ◽

Vol 279 (1) ◽

pp. F153-F160 ◽

Cited By ~ 14

Author(s):

Xiaoming Zhou ◽

I. Jeanette Lynch ◽

Shen-Ling Xia ◽

Charles S. Wingo

Keyword(s):

Channel Blocker ◽

Collecting Duct ◽

K Channel ◽

Cortical Collecting Duct ◽

Atpase Inhibitor

We studied the activation of H+-K+-ATPase by CO2 in the renal cortical collecting duct (CCD) of K-restricted animals. Exposure of microperfused CCD to 10% CO2 increased net total CO2 flux ( J t CO2 ) from 4.9 ± 2.1 to 14.7 ± 4 pmol · mm−1· min−1 ( P < 0.05), and this effect was blocked by luminal application of the H+-K+-ATPase inhibitor Sch-28080. In the presence of luminal Ba, a K channel blocker, exposure to CO2 still stimulated J t CO2 from 6.0 ± 1.0 to 16.8 ± 2.8 pmol · mm−1 · min−1 ( P < 0.01), but peritubular application of Ba inhibited the stimulation. CO2substantially increased 86Rb efflux (a K tracer marker) from 93.1 ± 23.8 to 249 ± 60.2 nm/s ( P < 0.05). These observations suggest that during K restriction 1) the enhanced H+-K+-ATPase-mediated acidification after exposure to CO2 is dependent on a basolateral Ba-sensitive mechanism, which is different from the response of rabbits fed a normal-K diet, where activation of the H+-K+-ATPase by exposure to CO2 is dependent on an apical Ba-sensitive pathway; and 2) K/Rb absorption via the apical H+-K+-ATPase exits through a basolateral Ba-sensitive pathway. Together, these data are consistent with the hypothesis of cooperation between H+-K+-ATPase-mediated acidification and K exit pathways in the CCD that regulate K homeostasis.

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Cloning and localization of a double-pore K channel, KCNK1: exclusive expression in distal nephron segments

AJP Renal Physiology ◽

10.1152/ajprenal.1997.273.4.f663 ◽

1997 ◽

Vol 273 (4) ◽

pp. F663-F666 ◽

Cited By ~ 10

Author(s):

Marcelo Orias ◽

Heino Velázquez ◽

Freeman Tung ◽

George Lee ◽

Gary V. Desir

Keyword(s):

Amino Acid ◽

Collecting Duct ◽

Human Kidney ◽

Distal Tubule ◽

Amino Acid Identity ◽

Northern Analysis ◽

K Channel ◽

Thick Ascending Limb ◽

Cortical Collecting Duct ◽

K Channels

The K-selective channel, TOK1, recently identified in yeast, displays the unusual structural feature of having two putative pore regions, in contrast to all previously cloned K channels. Using the TOK1 pore regions as probes, we identified a human kidney cDNA encoding a 337-amino acid protein (hKCNK1) with four transmembrane segments and two pore regions containing the signature sequence of K channels. Amino acid identity to TOK1 is only 15% overall but 40% at the pores. Northern analysis indicates high expression of a 1.9-kb message in brain > kidney >> heart. Nephron segment localization, carried out in rabbit by reverse transcription-polymerase chain reaction, reveals that KCNK1 is expressed in cortical thick ascending limb, connecting tubule, and cortical collecting duct. It was not detected in the proximal tubule, medullary thick ascending limb, distal convoluted tubule, and glomerulus. We conclude that KCNK1 is a unique, double-pore, mammalian K channel, distantly related to the yeast channel TOK1, that is expressed in distal tubule and is a candidate to participate in renal K homeostasis.

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Expression of a hypotonic swelling-activated Cl conductance during ontogeny of collecting duct epithelium

AJP Renal Physiology ◽

10.1152/ajprenal.1998.275.1.f25 ◽

1998 ◽

Vol 275 (1) ◽

pp. F25-F32 ◽

Cited By ~ 2

Author(s):

Stephan M. Huber ◽

Michael F. Horster

Keyword(s):

Collecting Duct ◽

Regulatory Volume Decrease ◽

Developmental Expression ◽

Cortical Collecting Duct ◽

Whole Cell ◽

Bath Solution ◽

Collecting Duct Epithelium ◽

Hypotonic Swelling ◽

Cl Conductance

Developmental expression of ion channels possibly participating in regulatory volume decrease was studied in rat embryonic ( day E17) and perinatal ( days P1–6) ureteric bud and in postnatal ( P9–14) cortical collecting duct cells in primary monolayer culture. In isotonic bath solution, whole cell conductance (in nS/10 pF) was highest in E17 (4.0 ± 0.5, n = 31) compared with P1–6 (2.0 ± 0.1, n = 16) and P9–14 (1.3 ± 0.2, n = 12) due to a decreasing contribution of a DIDS-sensitive Cl conductance, from E17 (2.8 ± 0.7, n = 12) to P1–6 (0.53 ± 0.07, n = 9) and P9–14 (0.05 ± 0.1, n = 7). Cl conductance in E17 exhibited a permselectivity of I ≈ Cl ≈ Br ≫ gluconate, and it activated time dependently. Hypotonic bath solution induced a large increase of whole cell conductance in P1–6 and in P9–14 but not in E17 (by 20.0 ± 3.7, 21.5 ± 5.5, and 4.9 ± 1.7; n = 11, 12, and 25, respectively) due to the activation of a time-dependently inactivating Cl conductance with a permselectivity of I ≥ Br > Cl ≫ gluconate. In conclusion, the expression of Cl channels, as studied in vitro, appears to shift from an apparently constitutively active embryonic to a hypotonic swelling-activated type during late embryonic development of the collecting duct.

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Reinterpretation of the RACTK1 K+ channel

AJP Cell Physiology ◽

10.1152/ajpcell.1997.272.1.c350 ◽

1997 ◽

Vol 272 (1) ◽

pp. C350-C354 ◽

Cited By ~ 15

Author(s):

B. Shmukler ◽

T. Sun ◽

C. Brugnara ◽

S. L. Alper

Keyword(s):

Collecting Duct ◽

Rabbit Kidney ◽

Antisense Strand ◽

K Channel ◽

Apical Surface ◽

Cortical Collecting Duct ◽

Channel Activity ◽

Reading Frame ◽

E Coli ◽

Collecting Duct Cells

The RACTK1 cDNA cloned from rabbit kidney cortical collecting duct cells was associated with inwardly rectifying pH-regulated K+ channel activity (M. Suzuki, K. Takahashi, M. [keda, H Hayakawa, A. Ogawa, Y. Kawaguchi, and O. Sakai. Nature Lond. 367: 642-645, 1994). The deduced amino acid sequence of the encoded novel polypeptide lacked the signature sequence of a K(+)-selective pore region but predicted a topography suggestive of the inward rectifier K+ channel family. In subsequent articles a RACTK1 epitope was immunolocalized to the apical surface of kidney collecting duct and to arteriolar smooth muscle [M. Suzuki, T. Takigawa, K. Kimura, C. Koseki, and M. Imai. Am. J. Physiol. 269 (Cell Physiol, 38): C496-C503, 1995], and apamin-sensitive K+ currents displaying Ca(2+)-dependent and voltage-independent activation accompanied stable heterologous overexpression of RACTK1 [M. Suzuki, M. Murata, M. Ikeda, T. Miyoshi, and M. Imai. Am. J. Physiol. 270 (Cell Physiol, 39): C964-C968, 1996]. We now report that the "RACTK1" open reading frame is a frame-shifted translation of the antisense strand of an Escherichia coli gene member of a coenzyme A transferase gene family. "RACTK1" mRNA was absent from tissues free of E. coli contamination, and the "RACTK1" gene was undetectable in Southern blots of human and rabbit genomic DNA. We conclude that the immunostaining patterns and Ca(2+)-activated K+ channel activity heretofore attributed to RACTK1 must be otherwise explained.

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