Vasopressin increases density of apical low-conductance K+ channels in rat CCD

1993 ◽  
Vol 264 (3) ◽  
pp. F502-F509 ◽  
Author(s):  
A. C. Cassola ◽  
G. Giebisch ◽  
W. Wang
Keyword(s):  
Collecting Duct ◽  
Phosphodiesterase Inhibitor ◽  
K Channel ◽  
Channel Activity ◽  
Dibutyryl Camp ◽  
Open Probability ◽  
Simultaneous Application ◽  
K Channels ◽  
Principal Cells ◽  
High K

The effect of arginine vasopressin (AVP) on the low-conductance K+ channel in the apical membrane of rat cortical collecting duct (CCD) principal cells from animals on a control and high-K+ diet was studied using patch-clamp techniques. AVP stimulated apical low-conductance K+ channel activity in both control and high-K+ animals: application of 110-220 pM AVP induced a significant increase in the density of low-conductance K+ channels. In the presence of phosphodiesterase inhibitor (3-isobutyl-1-methylxanthine), administration of 22 pM AVP also increased channel activity. The action of AVP on low-conductance K+ channel activity was mimicked by simultaneous application of forskolin and 3-isobutyl-1-methylxanthine. Exogenously applied N6,2'-O-dibutyryladenosine 3',5'-cyclic monophosphate (dibutyryl-cAMP, 0.4-0.8 mM) also increased apical low-conductance K+ channel activity. Since channel open probability (Po) was almost saturated in the absence of AVP, the increase of channel activity induced by AVP, forskolin, and dibutyryl-cAMP resulted predominantly from stimulating previously silent K+ channels. We conclude that AVP induces an increase of low-conductance K+ channel activity of principal cells in rat CCD by the stimulation of cAMP-dependent protein kinase. The AVP-induced increase of low-conductance K+ channel activity can thus significantly contribute to the hormone-induced K+ secretion in the rat CCD.

scholarly journals Membrane-delimited Inhibition of Maxi-K Channel Activity by the Intermediate Conductance Ca2+-activated K Channel

2006 ◽  
Vol 127 (2) ◽  
pp. 159-169 ◽  
Author(s):  
Jill Thompson ◽  
Ted Begenisich
Keyword(s):  
Single Channel ◽  
Expression System ◽  
Chemical Activation ◽  
K Channel ◽  
Channel Activity ◽  
Single Family ◽  
Open Probability ◽  
K Channels ◽  
Channel Proteins ◽  
K Activity

The complexity of mammalian physiology requires a diverse array of ion channel proteins. This diversity extends even to a single family of channels. For example, the family of Ca2+-activated K channels contains three structural subfamilies characterized by small, intermediate, and large single channel conductances. Many cells and tissues, including neurons, vascular smooth muscle, endothelial cells, macrophages, and salivary glands express more than a single class of these channels, raising questions about their specific physiological roles. We demonstrate here a novel interaction between two types of Ca2+-activated K channels: maxi-K channels, encoded by the KCa1.1 gene, and IK1 channels (KCa3.1). In both native parotid acinar cells and in a heterologous expression system, activation of IK1 channels inhibits maxi-K activity. This interaction was independent of the mode of activation of the IK1 channels: direct application of Ca2+, muscarinic receptor stimulation, or by direct chemical activation of the IK1 channels. The IK1-induced inhibition of maxi-K activity occurred in small, cell-free membrane patches and was due to a reduction in the maxi-K channel open probability and not to a change in the single channel current level. These data suggest that IK1 channels inhibit maxi-K channel activity via a direct, membrane-delimited interaction between the channel proteins. A quantitative analysis indicates that each maxi-K channel may be surrounded by four IK1 channels and will be inhibited if any one of these IK1 channels opens. This novel, regulated inhibition of maxi-K channels by activation of IK1 adds to the complexity of the properties of these Ca2+-activated K channels and likely contributes to the diversity of their functional roles.

Two types of K+ channel in thick ascending limb of rat kidney

1994 ◽  
Vol 267 (4) ◽  
pp. F599-F605 ◽  
Author(s):  
W. H. Wang
Keyword(s):  
Apical Membrane ◽  
Rat Kidney ◽  
Inhibitory Effect ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
K Channels ◽  
Inside Out

We have used the patch-clamp technique to study the apical K+ channels in the thick ascending limb (TAL) of the rat kidney. Two types of K+ channels, a low-conductance and an intermediate-conductance K+ channel, were identified in both cell-attached and inside-out patches. We confirmed the previously reported intermediate-conductance K+ channel (72 pS), which is inhibited by millimolar cell ATP, acidic pH, Ba2+, and quinidine (4). We now report a second K+ channel in apical membrane of the TAL. The slope conductance of this low-conductance K+ channel is 30 pS, and its open probability is 0.80 in cell-attached patches. This channel is not voltage dependent, and application of 2 mM ATP in the bath inhibits channel activity in inside-out patches. In addition, 250 microM glyburide, an ATP-sensitive K+ channel inhibitor, blocks channel activity, whereas the same concentration of glyburide has no inhibitory effect on the 72-pS K+ channel. Channel activity of the 30-pS K+ channel decreases rapidly upon excision of patches (channel run down). Application of 0.1 mM ATP and the catalytic subunit of adenosine 3',5'-cyclic monophosphate (cAMP)-dependent protein kinase A (PKA) restores channel activity. Furthermore, addition of 0.1 mM 8-(4-chlorophenylthio)-cAMP or 50-100 pM vasopressin in the cell-attached patches increases channel activity. In conclusion, two types of K+ channels are present in the apical membrane of TAL of rat kidney, and PKA plays an important role in modulation of the low-conductance K+ channel activity.

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.

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

1996 ◽  
Vol 271 (3) ◽  
pp. F588-F594 ◽  
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.

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

2014 ◽  
Vol 307 (7) ◽  
pp. F833-F843 ◽  
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.

scholarly journals Role of 20-HETE in mediating the effect of dietary K intake on the apical K channels in the mTAL

2001 ◽  
Vol 280 (2) ◽  
pp. F223-F230 ◽  
Author(s):  
Ruimin Gu ◽  
Yuan Wei ◽  
Houli Jiang ◽  
Michael Balazy ◽  
Wenhui Wang
Keyword(s):  
Gas Chromatography Mass Spectrometry ◽  
K Channel ◽  
Thick Ascending Limb ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
Deficient Diet ◽  
K Channels ◽  
Medullary Thick Ascending Limb ◽  
High K

We have used the patch-clamp technique to study the effect of dietary K intake on the apical K channels in the medullary thick ascending limb (mTAL) of rat kidneys. The channel activity, defined by the number of channels in a patch and the open probability ( NP o), of the 30- and 70-pS K channels, was 0.18 and 0.11, respectively, in the mTAL from rats on a K-deficient diet. In contrast, NP o of the 30- and 70-pS K channels increased to 0.60 and 0.80, respectively, in the tubules from animals on a high-K diet. The concentration of 20-hydroxyeicosatetraenoic acid (20-HETE) measured with gas chromatography-mass spectrometry was 0.8 pg/μg protein in the mTAL from rats on a high-K diet and increased significantly to 4.6 pg/μg protein in the tubules from rats on a K-deficient diet. Addition of N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS) or 17-octadecynoic acid (17-ODYA), agents that inhibit the formation of 20-HETE, had no significant effect on the activity of the 30-pS K channels. However, DDMS/17-ODYA significantly increased the activity of the apical 70-pS K channel from 0.11 to 0.91 in the mTAL from rats on a K-deficient diet. In contrast, inhibition of the cytochrome P-450 metabolism of arachidonic acid increased NP o from 0.64 to 0.81 in the tubules from animals on a high-K diet. Furthermore, the sensitivity of the 70-pS K channel to 20-HETE was the same between rats on a high-K diet and on a K-deficient diet. Finally, the pretreatment of the tubules with DDMS increased NP o of the 70-pS K channels in the mTAL from rats on a K-deficient diet to 0.76. We conclude that an increase in 20-HETE production is involved in reducing the activity of the apical 70-pS K channels in the mTAL from rats on a K-deficient diet.

scholarly journals The mechanosensitive BKα/β1 channel localizes to cilia of principal cells in rabbit cortical collecting duct (CCD)

2017 ◽  
Vol 312 (1) ◽  
pp. F143-F156 ◽  
Author(s):  
Rolando Carrisoza-Gaytán ◽  
Lijun Wang ◽  
Carlos Schreck ◽  
Thomas R. Kleyman ◽  
Wen-Hui Wang ◽  
...  
Keyword(s):  
Single Channel ◽  
Collecting Duct ◽  
High Amplitude ◽  
Bk Channels ◽  
Bk Channel ◽  
K Channel ◽  
Cortical Collecting Duct ◽  
Principal Cells ◽  
High K ◽  
Dependent Flow

Within the CCD of the distal nephron of the rabbit, the BK (maxi K) channel mediates Ca2+- and/or stretch-dependent flow-induced K+ secretion (FIKS) and contributes to K+ adaptation in response to dietary K+ loading. An unresolved question is whether BK channels in intercalated cells (ICs) and/or principal cells (PCs) in the CCD mediate these K+ secretory processes. In support of a role for ICs in FIKS is the higher density of immunoreactive apical BKα (pore-forming subunit) and functional BK channel activity than detected in PCs, and an increase in IC BKα expression in response to a high-K+ diet. PCs possess a single apical cilium which has been proposed to serve as a mechanosensor; direct manipulation of cilia leads to increases in cell Ca2+ concentration, albeit of nonciliary origin. Immunoperfusion of isolated and fixed CCDs isolated from control K+-fed rabbits with channel subunit-specific antibodies revealed colocalization of immunodetectable BKα- and β1-subunits in cilia as well as on the apical membrane of cilia-expressing PCs. Ciliary BK channels were more easily detected in rabbits fed a low-K+ vs. high-K+ diet. Single-channel recordings of cilia revealed K+ channels with conductance and kinetics typical of the BK channel. The observations that 1) FIKS was preserved but 2) the high-amplitude Ca2+ peak elicited by flow was reduced in microperfused CCDs subject to pharmacological deciliation suggest that cilia BK channels do not contribute to K+ secretion in this segment, but that cilia serve as modulators of cell signaling.

Arachidonic acid inhibits the secretory K+ channel of cortical collecting duct of rat kidney

1992 ◽  
Vol 262 (4) ◽  
pp. F554-F559 ◽  
Author(s):  
W. Wang ◽  
A. Cassola ◽  
G. Giebisch
Keyword(s):  
Arachidonic Acid ◽  
Oleic Acid ◽  
Unsaturated Fatty Acids ◽  
Enzyme Inhibitor ◽  
Collecting Duct ◽  
K Channel ◽  
Cortical Collecting Duct ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Open Probability

We used the patch-clamp technique to study the effects of arachidonic acid (AA) on the 35-pS secretory K+ channel in the apical membrane of rat cortical collecting duct (CCD). Application of 10 microM AA reversibly reduced channel activity to 1% of the control value [sum of open probability (NPo) decreased from 3.8 to 0.04]. AA inhibits the apical 35-pS K+ channel directly, because application of indomethacin (an inhibitor of cyclooxygenase), nordihydroguaiaretic acid (an enzyme inhibitor of lipoxygenase), and clotrimazole (an inhibitor of epoxygenase) failed to antagonize the AA-induced blocking effect on K+ channel activity. Oleic acid, a cis-unsaturated acid, also blocks K+ channel activity. However, the inhibitory constant (Ki) of oleic acid (5.1 microM) is significantly higher than that of AA (2.6 microM). These results indicate that AA and cis-unsaturated fatty acids are involved in downregulating the apical secretory K+ channel of rat CCD.

The Role of 20-Hete in Mediating the Effect of Diatary K Intake on the Apical K Channels in the Mtal.

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 710-710
Author(s):  
WenHui Wang ◽  
RuiMin Gu ◽  
Yuan Wei ◽  
Michael Balazy ◽  
Houli Jiang
Keyword(s):  
K Channel ◽  
Thick Ascending Limb ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Deficient Diet ◽  
K Channels ◽  
Medullary Thick Ascending Limb ◽  
A Value ◽  
High K

P95 We have used the patch clamp technique to study the effect of dietary-K intake on the apical K channels in the medullary thick ascending limb (mTAL) of rat kidneys. The channel activity, defined by NPo, of the 30 pS and 70 pS K channel was 0.18 and 0.11 in the mTAL from rats on a K-deficient diet, respectively. In contrast, NPo of the 30 pS and the 70 pS K channels increased to 0.60 and 0.80 in the tubules from animals on a high-K diet, respectively. We have also used GC/MC to measure the intracellular production of 20-hydroxyeicosanotetraenoic acid (20-HETE) in the mTAL. The concentration of 20-HETE was 0.8 pg/μg protein in the mTAL from rats on a high-K diet and increased significantly to 4.6 pg/μg protein in the tubules from rats on a K-deficient diet. Addition of N-methylsulfonyl-12,12-dibromododec-11-enamide (DDMS) or 17-octadecynoic acid (17ODYA), agents which inhibit the formation of 20-HETE, had no significant effect on the activity of the 30 pS K channels. However, DDMS/17ODYA significantly increased the activity of the apical 70 pS K channel from 0.11 to 0.91 in the mTAL from rats on a K-deficient diet. In contrast, inhibition of the cytochrome P450 metabolism of arachidonic acid (AA) increased NPo from 0.64 to 0.81 in the tubules from animals on a high-K diet. Furthermore, the concentration of 20-HETE required to block the channel activity by 50% was the same in the mTAL from rats on a high K diet as that on a K-deficient diet. This indicates that the diminished response of the 70 pS K channel to the inhibition of P450 metabolism of AA is not the result of decreasing 20-HETE sensitivity in the mTAL from rats on a high K diet. Finally, the pretreatment of the tubules with DDMS increased NPo of the 70 pS K channels in the mTAL from rats on a K-deficient diet to 0.76, a value which is not significantly different from the NPo in the tubules from rats on a high-K diet. We conclude that an increase in 20-HETE production is involved in reducing the activity of the apical 70 pS K channels in the mTAL from rats on a K-deficient diet.

scholarly journals Regulation of apical K and Na channels and Na/K pumps in rat cortical collecting tubule by dietary K.

1994 ◽  
Vol 104 (4) ◽  
pp. 693-710 ◽  
Author(s):  
L G Palmer ◽  
L Antonian ◽  
G Frindt
Keyword(s):  
K Channel ◽  
Na Channel ◽  
Sk Channels ◽  
Na Channels ◽  
Channel Activity ◽  
Patch Clamp Technique ◽  
Open Probability ◽  
High K ◽  
Collecting Tubule ◽  
Cortical Collecting Tubule

The patch-clamp technique was used to study the properties and the density of conducting K and Na channels in the apical membrane of rat cortical collecting tubule. The predominant K channel observed in cell-attached patches (SK channels) had an outward single-channel conductance (with LiCl in the pipette) of 10 pS. The inward conductance (with KCl in the pipette) was 42 pS. The channel had a high open probability that increased with depolarization. Kinetic analysis indicated the presence of a single open state and two closed states. Increasing K intake by maintaining animals on a high K diet for 12-16 d increased the number of SK channels per patch by threefold (0.7-2.0/patch) over control levels. In addition, conducting Na-selective channels, which were not observed in control animals, were seen at low density (0.5/patch). These channels had properties similar to those observed when the animals were on a low Na diet, except that the mean open probability (0.84) was higher. In other experiments, the whole-cell patch clamp technique was used to measure Na channel activity (as amiloride-sensitive current, INa) and Na pump activity (as ouabain-sensitive current, Ipump). In animals on a high K diet, INa was greater than in controls but much less than in rats on a low Na diet. Ipump was greater after K loading than in controls or Na-depleted animals. These K diet-dependent effects were not accompanied by a significant increase in plasma aldosterone concentrations. To further investigate the relationship between K channel activity and mineralocorticoids, rats were maintained on a low Na diet to increase endogenous aldosterone secretion. Under these conditions, no increase in SK channel density was observed, although there was a large increase in the number of Na channels (to 2.7/patch). Aldosterone was also administered exogenously through osmotic minipumps. As with the low Na diet, there was no change in the density of conducting SK channels, although Na channel activity was induced. These results suggest that SK channels, Na channels and Na/K pumps are regulated during changes in K intake by factors other than aldosterone.

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