Dual Role of Prostaglandins (PGE 2 ) in Regulation of Channel Density and Open Probability of Epithelial Na + Channels in Frog Skin ( R. pipiens )

1997 ◽  
Vol 155 (1) ◽  
pp. 75-87 ◽  
Author(s):  
W.J. Els ◽  
S.I. Helman
Keyword(s):  
Frog Skin ◽  
Dual Role ◽  
Na Channels ◽  
Open Probability ◽  
Channel Density ◽  
Epithelial Na Channels

S-adenosyl-l-homocysteine hydrolase is necessary for aldosterone-induced activity of epithelial Na+ channels

2001 ◽  
Vol 281 (3) ◽  
pp. C773-C785 ◽  
Author(s):  
James D. Stockand ◽  
Shawn Zeltwanger ◽  
Hui-Fang Bao ◽  
Andrea Becchetti ◽  
Roger T. Worrell ◽  
...  
Keyword(s):  
Cell Line ◽  
Transition Rate ◽  
Critical Role ◽  
Na Channels ◽  
Open Probability ◽  
Epithelial Na Channels ◽  
Open States ◽  
Kinetics Of ◽  
Expression And Activity

The A6 cell line was used to study the role of S-adenosyl-l-homocysteine hydrolase (SAHHase) in the aldosterone-induced activation of the epithelial Na+channel (ENaC). Because aldosterone increases methylation of several different molecules, and because this methylation is associated with increased Na+ reabsorption, we tested the hypothesis that aldosterone increases the expression and activity of SAHHase protein. The rationale for this work is that general methylation may be promoted by activation of SAHHase, the only enzyme known to metabolize SAH, a potent end-product inhibitor of methylation. Although aldosterone increased SAHHase activity, steroid did not affect SAHHase expression. Antisense SAHHase oligonucleotide decreased SAHHase expression and activity. Moreover, this oligonucleotide, as well as a pharmacological inhibitor of SAHHase, decreased aldosterone-induced activity of ENaC via a decrease in ENaC open probability. The kinetics of ENaC in cells treated with antisense plus aldosterone were similar to those reported previously for the channel in the absence of steroid. This is the first report showing that active SAHHase, in part, increases ENaC open probability by reducing the transition rate from open states in response to aldosterone. Thus aldosterone-induced SAHHase activity plays a critical role in shifting ENaC from a gating mode with short open and closed times to one with longer open and closed times.

scholarly journals Blocker-related changes of channel density. Analysis of a three-state model for apical Na channels of frog skin.

1990 ◽  
Vol 95 (4) ◽  
pp. 647-678 ◽  
Author(s):  
S I Helman ◽  
L M Baxendale
Keyword(s):  
Frog Skin ◽  
Noise Analysis ◽  
Kinetic Scheme ◽  
State Model ◽  
Na Channel ◽  
Na Channels ◽  
Na Transport ◽  
Open Probability ◽  
Wide Range ◽  
Three State Model

Blocker-induced noise analysis of apical membrane Na channels of epithelia of frog skin was carried out with the electroneutral blocker (CDPC, 6-chloro-3,5-diamino-pyrazine-2-carboxamide) that permitted determination of the changes of single-channel Na currents and channel densities with minimal inhibition of the macroscopic rates of Na transport (Baxendale, L. M., and S. I. Helman. 1986. Biophys. J. 49:160a). Experiments were designed to resolve changes of channel densities due to mass law action (and hence the kinetic scheme of blocker interaction with the Na channel) and to autoregulation of Na channel densities that occur as a consequence of inhibition of Na transport. Mass law action changes of channel densities conformed to a kinetic scheme of closed, open, and blocked states where blocker interacts predominantly if not solely with open channels. Such behavior was best observed in "pulse" protocol experiments that minimized the time of exposure to blocker and thus minimized the contribution of much longer time constant autoregulatory influences on channel densities. Analysis of data derived from pulse, staircase, and other experimental protocols using both CDPC and amiloride as noise-inducing blockers and interpreted within the context of a three-state model revealed that Na channel open probability in the absence of blocker averaged near 0.5 with a wide range among tissues between 0.1 and 0.9.

Epithelial Na channels and short-term renal response to salt deprivation

2002 ◽  
Vol 283 (4) ◽  
pp. F717-F726 ◽  
Author(s):  
Gustavo Frindt ◽  
Tiffany McNair ◽  
Anke Dahlmann ◽  
Emily Jacobs-Palmer ◽  
Lawrence G. Palmer
Keyword(s):  
Distal Tubule ◽  
Treated Group ◽  
Na Channel ◽  
Na Channels ◽  
Nacl Transport ◽  
Drug Concentrations ◽  
Epithelial Na Channels ◽  
Late Evening ◽  
Excretion Rates

To test the role of epithelial Na channels in the day-to-day regulation of renal Na excretion, rats were infused via osmotic minipumps with the Na channel blocker amiloride at rates that achieved drug concentrations of 2–5 μM in the lumen of the distal nephron. Daily Na excretion rates were unchanged, although amiloride-treated animals tended to excrete more Na in the afternoon and less in the late evening than controls. When the rats were given a low-Na diet, Na excretion rates were elevated in the amiloride-treated group within 4 h and remained higher than controls for at least 48 h. Adrenalectomized animals responded similarly to the low-Na diet. In contrast, rats infused with polythiazide at rates designed to inhibit NaCl transport in the distal tubule were able to conserve Na as well as did the controls. Injection of aldosterone (2 μg/100 g body wt) decreased Na excretion in control animals after a 1-h delay. This effect was largely abolished in amiloride-treated rats. On the basis of quantitative analysis of the results, we conclude that activation of amiloride-sensitive channels by mineralocorticoids accounts for 50–80% of the immediate natriuretic response of the kidney to a reduction in Na intake. Furthermore, the channels are necessary to achieve minimal rates of Na excretion during more chronic Na deprivation.

scholarly journals The Role of Pre-H2 Domains of α- and δ-Epithelial Na+Channels in Ion Permeation, Conductance, and Amiloride Sensitivity

2003 ◽  
Vol 279 (9) ◽  
pp. 8428-8440 ◽  
Author(s):  
Hong-Long Ji ◽  
LaToya R. Bishop ◽  
Susan J. Anderson ◽  
Catherine M. Fuller ◽  
Dale J. Benos
Keyword(s):  
Ion Permeation ◽  
Na Channels ◽  
Epithelial Na Channels

Mineralocorticoid regulation of epithelial Na+ channels is maintained in a mouse model of Liddle's syndrome

2003 ◽  
Vol 285 (2) ◽  
pp. F310-F318 ◽  
Author(s):  
Anke Dahlmann ◽  
Sylvain Pradervand ◽  
Edith Hummler ◽  
Bernard C. Rossier ◽  
Gustavo Frindt ◽  
...  
Keyword(s):  
Single Cells ◽  
Noise Analysis ◽  
Channel Noise ◽  
Na Channels ◽  
Open Probability ◽  
Whole Cell ◽  
Liddle’S Syndrome ◽  
Epithelial Na Channels ◽  
Liddle's Syndrome ◽  
Single Channel Currents

Currents through epithelial Na channels (ENaCs) were measured in the cortical collecting tubule (CCT) of mice expressing truncated β-subunits of ENaC, reproducing one of the mutations found in human patients with Liddle's syndrome. Tubules were isolated from mice homozygous for the Liddle mutation (L/L) and from wild-type (WT) littermates. Amiloride-sensitive currents ( INa) from single cells were recorded under whole cell clamp conditions. CCTs from mice kept under control conditions and fed a diet with normal levels of Na had very small INas (WT: 18 ± 13 pA; L/L: 22 ± 8 pA at Vm = –100 mV) that were not different in WT and L/L animals. However, the L/L mice had much larger currents when the animals were fed a low-Na diet (WT: 256 ± 127 pA; L/L: 1,820 ± 330 pA) or infused with aldosterone (WT: 285 ± 63 pA; L/L: 1,600 ± 280 pA). Currents from L/L mice were also larger when animals were pretreated with a high-K diet but not when the CCTs were stimulated in vitro with 8-CTP-cAMP. Noise analysis of amiloride-induced fluctuations in INa showed that single-channel currents at Vm = 0 mV were slightly smaller in L/L mice (WT: 0.33 pA; L/L: 0.24 pA). This difference could be attributed to a decrease in driving force since current-voltage analysis indicated that intracellular Na was increased in the L/L animals. Analysis of spontaneous channel noise indicated that the open probability was similar in the two genotypes(WT: 0.77; L/L: 0.80). Thus the increase in whole cell current is attributed to a difference in the density of conducting channels.

Activation of epithelial Na+ channels by protein kinase A requires actin filaments

1993 ◽  
Vol 265 (1) ◽  
pp. C224-C233 ◽  
Author(s):  
A. G. Prat ◽  
A. M. Bertorello ◽  
D. A. Ausiello ◽  
H. F. Cantiello
Keyword(s):  
Protein Kinase ◽  
Actin Filaments ◽  
Actin Polymerization ◽  
Na Channel ◽  
Na Channels ◽  
Channel Activation ◽  
Epithelial Na Channels ◽  
Inside Out ◽  
Kinase A

We have recently demonstrated a novel role for "short" actin filaments, a distinct species of polymerized actin different from either monomeric (G-actin) or long actin filaments (F-actin), in the activation of epithelial Na+ channels. In the present study, the role of actin in the activation of apical Na+ channels by the adenosine 3',5'-cyclic monophosphate-dependent protein kinase A (PKA) was investigated by patch-clamp techniques in A6 epithelial cells. In excised inside-out patches, addition of deoxyribonuclease I, which prevents actin polymerization, inhibited Na+ channel activation mediated by PKA. Disruption of endogenous actin filament organization with cytochalasin D for at least 1 h prevented the PKA-mediated activation of Na+ channels but not activation following the addition of actin to the cytosolic side of the patch. To assess the role of PKA on actin filament organization, actin was used as a substrate for the specific phosphorylation by the PKA. Actin was phosphorylated by PKA with an equilibrium stoichiometry of 2:1 mol PO4-actin monomer. Actin was phosphorylated in its monomeric form, but only poorly once polymerized. Furthermore, phosphorylated actin reduced the rate of actin polymerization. Thus actin allowed to polymerize for at least 1 h in the presence of PKA and ATP to obtain phosphorylated actin filaments induced Na+ channel activity in excised inside-out patches, in contrast to actin polymerized either in the absence of PKA or in the presence of PKA plus a PKA inhibitor (nonphosphorylated actin filaments). This was also confirmed by using purified phosphorylated G-actin incubated in a polymerizing buffer for at least 1 h at 37 degrees C. These data suggest that the form of actin required for Na+ channel activation (i.e., "short" actin filaments) may be favored by the phosphorylation of G-actin and may thus mediate or facilitate the activation of Na+ channels by PKA.

scholarly journals Role of epithelial Na+channels in endothelial function

2015 ◽  
Vol 129 (2) ◽  
pp. 290-297 ◽  
Author(s):  
Dongqing Guo ◽  
Shenghui Liang ◽  
Su Wang ◽  
Chengchun Tang ◽  
Bin Yao ◽  
...  
Keyword(s):  
Endothelial Function ◽  
Na Channels ◽  
Epithelial Na Channels

scholarly journals Regulation by Na+ and Ca2+ of renal epithelial Na+ channels reconstituted into planar lipid bilayers.

1995 ◽  
Vol 106 (3) ◽  
pp. 445-466 ◽  
Author(s):  
I I Ismailov ◽  
B K Berdiev ◽  
D J Benos
Keyword(s):  
Protein Kinase ◽  
Lipid Bilayers ◽  
Single Channel ◽  
Single Channels ◽  
Planar Lipid Bilayers ◽  
Na Channels ◽  
Channel Activity ◽  
Open Probability ◽  
Epithelial Na Channels ◽  
Cis And Trans

Purified bovine renal epithelial Na+ channels when reconstituted into planar lipid bilayers displayed a specific orientation when the membrane was clamped to -40 mV (cis-side) during incorporation. The trans-facing portion of the channel was extracellular (i.e., amiloride-sensitive), whereas the cis-facing side was intracellular (i.e., protein kinase A-sensitive). Single channels had a main state unitary conductance of 40 pS and displayed two subconductive states each of 12-13 pS, or one of 12-13 pS and the second of 24-26 pS. Elevation of the [Na+] gradient from the trans-side increased single-channel open probability (Po) only when the cis-side was bathed with a solution containing low [Na+] (< 30 mM) and 10-100 microM [Ca2+]. Under these conditions, Po saturated with increasing [Na+]trans. Buffering of the cis compartment [Ca2+] to nearly zero (< 1 nM) with 10 mM EGTA increased the initial level of channel activity (Po = 0.12 +/- 0.02 vs 0.02 +/- 0.01 in control), but markedly reduced the influence of both cis- and trans-[Na+] on Po. Elevating [Ca2+]cis at constant [Na+] resulted in inhibition of channel activity with an apparent [KiCa2+] of 10-100 microM. Protein kinase C-induced phosphorylation shifted the dependence of channel Po on [Ca2+]cis to 1-3 microM at stationary [Na+]. The direct modulation of single-channel Po by Na+ and Ca2+ demonstrates that the gating of amiloride-sensitive Na2+ channels is indeed dependent upon the specific ionic environment surrounding the channels.

Hypoxia-Induced Inhibition of Epithelial Na+Channels in the Lung. Role of Nedd4-2 and the Ubiquitin-Proteasome Pathway

2014 ◽  
Vol 50 (3) ◽  
pp. 526-537 ◽  
Author(s):  
Thomas Gille ◽  
Nadia Randrianarison-Pellan ◽  
Arnaud Goolaerts ◽  
Nicolas Dard ◽  
Yurdagül Uzunhan ◽  
...  
Keyword(s):  
Na Channels ◽  
Ubiquitin Proteasome Pathway ◽  
Epithelial Na Channels ◽  
Ubiquitin Proteasome ◽  
Proteasome Pathway
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