Cellular K+ permeation across the cortical collecting tubule: effects of Na+-K+ pump inhibition and membrane depolarization

1984 ◽  
Vol 246 (4) ◽  
pp. F467-F475 ◽  
Author(s):  
J. B. Stokes
Keyword(s):  
Rate Coefficient ◽  
Compartment Model ◽  
Membrane Depolarization ◽  
Experimental Conditions ◽  
Simple Diffusion ◽  
Collecting Tubule ◽  
In Series ◽  
Diffusion Voltage ◽  
K Permeability ◽  
Cortical Collecting Tubule

These experiments examined the possibility that alterations in cell cation content and/or membrane voltage could influence cell K+ permeability of the cortical collecting tubule. Using the amiloride-treated isolated perfused rabbit cortical collecting tubule, ouabain or a K+-free bath reduced the magnitude of the K+ diffusion voltage. In addition, both methods of Na+-K+-ATPase inhibition reduced the K+ efflux (lumen-to-bath) rate coefficient (KK) without affecting the Na+ efflux rate coefficient. The magnitude of the reduction of KK could not be explained by a model of simple diffusion across two membranes in series even if the intracellular voltage were abolished. Thus, pump inhibition reduced cell K+ permeability. To determine whether membrane depolarization could induce a change in membrane permeability, [K+] was increased to 20 mM in both perfusate and bath. The reduction in KK was within the range predicted by the three-compartment model (36%). Differential membrane depolarization by raising lumen [K+] or bath [K+] produced disparate results. Apical depolarization reduced KK but basolateral depolarization did not. Taken together these results indicate that intracellular ion content may play a major role in regulating cell K+ permeability independent of voltage-dependent effects. In addition, under these experimental conditions, the apical membrane may be the rate-limiting barrier to cellular transfer.

Pathways of K+ permeation across the rabbit cortical collecting tubule: effect of amiloride

1984 ◽  
Vol 246 (4) ◽  
pp. F457-F466 ◽  
Author(s):  
J. B. Stokes
Keyword(s):  
Rate Coefficient ◽  
Single File ◽  
Collecting Tubule ◽  
Before And After ◽  
Transepithelial Voltage ◽  
Diffusion Voltage ◽  
K Permeability ◽  
K Transport ◽  
Rabbit Cortical Collecting Tubule ◽  
Cortical Collecting Tubule

These experiments were designed to examine passive K+ transport by the rabbit cortical collecting tubule. Potassium diffusion voltages were used to assess the presence of apical and basolateral K+ conductances. With amiloride (0.1 mM) in the lumen, reproducible K+ diffusion voltages from both the lumen and bath were obtained. Amiloride enhanced the magnitude of these voltage deflections (delta VT). There were time-dependent increases in the K+ diffusion voltage but the steady-state values were highly reproducible in the same tubule. In the amiloride-treated tubules, delta VT induced by raising bath [K+] to 20 mM was larger than that produced by the same increase in lumen [K+]. To evaluate whether the amiloride-treated tubule had, as suggested by the K+ diffusion voltages, substantial K+ permeabilities on both apical and basolateral membranes, the K+ rate coefficient (lumen-to-bath, KK) was measured before and after amiloride treatment. The amiloride-induced increase in KK, from 66 +/- 6 to 205 +/- 35 nm/s, was significantly larger than could be accounted for by the changes in transepithelial voltage or membrane voltages alone. This discrepancy could be due to single-file diffusion across the apical membrane and/or the (secondary) enhancement of K+ permeability following inhibition of Na+ transport.

Effects of inhibitors of Cl conductance on Cl self-exchange in rabbit cortical collecting tubule

1986 ◽  
Vol 251 (6) ◽  
pp. F1009-F1017
Author(s):  
K. Tago ◽  
D. H. Warden ◽  
V. L. Schuster ◽  
J. B. Stokes
Keyword(s):  
Rate Coefficient ◽  
Basolateral Membrane ◽  
Experimental Conditions ◽  
Conductive Pathway ◽  
Tracer Movement ◽  
Collecting Tubule ◽  
In Series ◽  
Transepithelial Voltage ◽  
Paracellular Diffusion ◽  
Cl Conductance

Electroneutral vs. conductive pathways of Cl transport were examined by measuring transepithelial conductance (GT) and the lumen-to-bath 36Cl rate coefficient (KCl). Experimental conditions minimized both Cl-HCO3 exchange [HCO3/CO2-free, N-2-hydroxyethylpiperazine-N'-2-ethane-sulfonic acid (HEPES)-buffered solutions] and the electrical driving force for paracellular Cl diffusion (amiloride in the perfusate, transepithelial voltage near zero). Two agents known to inhibit Cl conductances in other epithelia, anthracene-9-carboxylate (9AC, 1 mM) and diphenylamine carboxylate (DPC, 0.1-0.5 mM) reversibly reduced GT and KCl when added to the bath. Both reduced KCl to values consistent with paracellular diffusion. Bath DPC had no effect on GT in the presence of 4 mM lumen Ba2+, suggesting that the DPC-sensitive conductance is in series with an apical K conductance, i.e., resides on the basolateral membrane. Lumen DPC also reduced GT and KCl, but was less potent than bath DPC. Because the lumen DPC effect on GT was also blocked by lumen Ba2+, lumen DPC probably inhibits a basolateral Cl conductance. K removal and ouabain (0.5 mM) had no effect on KCl, suggesting that Cl tracer movement is not predominantly through the principal cell. We assume that these agents are inhibiting Cl conductive pathways and propose a model in which transcellular Cl movement through the intercalated cell occurs via an apical electroneutral entry step in series with a basolateral conductive pathway.

Patterns of K+ permeation following inhibition of Na+ transport in rabbit cortical collecting tubule

1986 ◽  
Vol 250 (1) ◽  
pp. F120-F126 ◽  
Author(s):  
J. B. Stokes
Keyword(s):  
Apical Membrane ◽  
Na Transport ◽  
Transcellular Pathway ◽  
Collecting Tubule ◽  
Before And After ◽  
K Secretion ◽  
Pg E2 ◽  
Collecting Tubules ◽  
K Permeability ◽  
Cortical Collecting Tubule

The passive (lumen-to-bath) K+ permeation (KK) of rabbit cortical collecting tubules was measured before and after inhibition of Na+ transport. Inhibition of the Na-K pump with ouabain reduced KK. This result contrasts sharply with the previously described increase in KK observed following inhibition of Na+ transport with amiloride. These opposite changes in KK are owing to the fact that a substantial component of the lumen-to-bath K+ permeation involves a transcellular pathway. Amiloride, because it hyperpolarizes the apical membrane, increases KK; ouabain, because it depolarizes the cell, decreases KK. Previous results have also suggested that the cell K+ permeability is secondarily altered by these agents so that the changes in voltage and permeability are additive. These patterns of changes in KK were used to evaluate the mechanism of action of two agents that partially inhibit Na+ transport: vasopressin and prostaglandin (PG) E2. Their effect on KK was qualitatively similar to that of amiloride. In amiloride-treated tubules, neither vasopressin nor PGE2 altered KK. Neither did they alter the normal reduction in KK caused by pump inhibition. Thus they did not have any direct effect on K+ permeability. These results are consistent with the thesis that vasopressin and PGE2 inhibit Na+ absorption by reducing apical membrane permeability. The relation between the regulation of Na+ absorption and K+ permeation may have important implications for the regulation of K+ secretion by the cortical collecting tubule.

Handling of angiotensin II and oxytocin by renal tubular segments perfused in vitro

1977 ◽  
Vol 232 (4) ◽  
pp. F319-F324 ◽  
Author(s):  
D. R. Peterson ◽  
S. Oparil ◽  
G. Flouret ◽  
F. A. Carone
Keyword(s):  
Angiotensin Ii ◽  
Rabbit Kidney ◽  
Experimental Conditions ◽  
Radioactive Label ◽  
Collecting Tubule ◽  
Pars Recta ◽  
Renal Tubular ◽  
Hydrolysis Of ◽  
Cortical Collecting Tubule

In order to study renal tubular handling of two small peptide hormones, [14c]angiotensin II ([14C]AII) and [3H]oxytocin ([3H]OT) were microperfused through rabbit kidney tubule segments in vitro. The reabsorption and tubular sequestration of radioactive label were determined, and the collection fluid was electrophoretically analyzed. The data suggest that [14C]AII is extensively hydrolyzed in the pars recta of the nephron and is rapidly reabsorbed across the tubular epithelium. Under similar experimental conditions, hydrolysis of [3H]OT was not observed in either the proximal straight or cortical collecting tubule segment, and the rate of reabsorption was low. Thus, tubular handling of OT appears to differ from that of AII, probably because of differences in molecular structure.

Na and K transport across the cortical and outer medullary collecting tubule of the rabbit: evidence for diffusion across the outer medullary portion

1982 ◽  
Vol 242 (5) ◽  
pp. F514-F520 ◽  
Author(s):  
J. B. Stokes
Keyword(s):  
Rate Coefficient ◽  
Renal Medulla ◽  
Rate Coefficients ◽  
Efflux Rate ◽  
Chemical Gradients ◽  
Na Efflux ◽  
Collecting Tubule ◽  
K Transport ◽  
Cortical Collecting Tubule

The rabbit collecting tubule displays functional axial heterogeneity with respect to Na ion transport. The present experiments compared cortical collecting tubule (CCT) and outer medullary collecting tubule (OMCT) Na and K transport. Na efflux across the CCT was inhibited by ouabain, whereas Na efflux across the OMCT was smaller and unaffected by ouabain. Assessment of the equivalent conductivities of Na and K across the CCT by imposition of a Na-K bi-ionic gradient demonstrated a higher K/Na conductivity across the CCT than would be predicted from their respective limiting equivalent conductivities in water. In contrast, the ratio of their conductivities across OMCT were not different than would be predicted by their ratio in water. The "selective" nature of the Na and K pathways across CCT was confirmed by measuring the tracer efflux rate coefficients. In the amiloride-treated CCT the K/Na rate coefficient ratio was 9.8 +/- 1.5; this ratio across the OMCT was 1.51 +/- 0.10. The latter value is not different from the ratio of the mobilities of these ions in water. The diffusional nature of Na and K transfer across OMCT was confirmed by the demonstration of the concentration-independent Na efflux rate coefficient and the demonstration of appropriate net Na and K transepithelial flows in response to imposition of oppositely directed chemical gradients. Although the permeability of the OMCT is low, the chemical gradients found in vivo might be sufficient to effect some K absorption and Na secretion without completely dissipating the steep gradients generated by the CCT. These transport characteristics might be important in the regulation of Na excretion and K recycling into the renal medulla.

Ionic conductive properties and electrophysiology of the rabbit cortical collecting tubule

1982 ◽  
Vol 243 (1) ◽  
pp. F81-F95 ◽  
Author(s):  
R. G. O'Neil ◽  
E. L. Boulpaep
Keyword(s):  
Cell Membrane ◽  
Tight Junction ◽  
Apical Cell ◽  
Apical Cell Membrane ◽  
Electrophysiological Properties ◽  
Basolateral Cell Membrane ◽  
Collecting Tubule ◽  
Conductive Properties ◽  
K Permeability ◽  
Cortical Collecting Tubule

The Na, K, and Cl conductive properties and the electrophysiological variability of the rabbit isolated cortical collecting tubule were assessed by evaluating the effect of single-ion substitutions on the transepithelial potential difference, Vte, and the transepithelial conductance, Gte. The Na permeability (and conductance) of the tight junction and basolateral cell membrane appeared to be low. However, a significant but variable amiloride-sensitive Na conductance was identified at the apical cell membrane. Although this Na conductance accounts for less than 10% of the Gte, variations in this conductance caused major alterations in the active transepithelial Na current and the Vte. A highly variable K permeability (and conductance) was also identified at the apical cell border and may account for some of the variability in Vte and Gte. This probably provides a pathway for K secretion from cell to lumen. The K permeability of the tight junction and basolateral cell membrane appeared to be relatively low. In contrast, the Cl permeability (and conductance) of the tight junction, and perhaps of the basolateral cell membrane, appeared to be high but variable and to account for the major fraction of the Gte and its variability. It is concluded that variations in the Na and K conductance of the apical cell membrane and the Cl conductance of the tight junction and basolateral cell membrane predominantly account for the variations in the electrophysiological properties of the cortical collecting tubule.

Validation of a monetary Taylor Aggression Paradigm: Associations with trait aggression and role of provocation sequence

2020 ◽  
Author(s):  
J Konzok ◽  
L Kreuzpointner ◽  
GI Henze ◽  
L Wagels ◽  
C Kärgel ◽  
...  
Keyword(s):  
Random Sequence ◽  
Reactive Aggression ◽  
Reaction Time Task ◽  
Competitive Reaction ◽  
Experimental Conditions ◽  
Fixed Sequence ◽  
Taylor Aggression Paradigm ◽  
Trait Aggression ◽  
Significant Difference ◽  
In Series

© 2020 Elsevier Inc. The Taylor Aggression Paradigm (TAP) is widely used to measure reactive aggression in laboratory settings. While modified versions (mTAPs) with various stimulus characteristics (shocks, noise, pressure, heat) have already been established, a modified version with monetary stimuli has only been introduced very recently. In this experiment, 209 young healthy participants (104 males, 105 females) completed a mock Competitive Reaction Time Task (CRTT) with a fictional opponent with preprogrammed 40 win and 60 lose trials. In lose trials, participants were provoked by subtracting a low (0–20 euro cents), medium (30–60 cents) or high (70–90 cents) amount of money from their fictitious account. Provocation stimuli were either presented randomly or in a fixed sequence (experimental conditions). In contrast to a random sequence, the fixed sequence was generated by repeating trials from the same provocation category in series of three. Linear mixed models (LMMs) considering aggression trajectories revealed significant effects of provocation (low, medium, high) and trait aggression (K-FAF) on reactive aggression. Men showed significantly higher reactive aggression levels than women. In regard to provocation sequence, we found no significant difference in reactive aggression between the random vs. fixed stimulus sequences. The findings provide new evidence supporting the view that the monetary mTAP is able to induce as well as capture reactive aggression in the laboratory. Additionally, we found no advantage of a fixed sequence as the level of reactive aggression in a given trial appeared to be mainly predicted by the preceding provocation trial.

Amiloride-sensitive sodium channels in rabbit cortical collecting tubule primary cultures

1991 ◽  
Vol 261 (6) ◽  
pp. F933-F944 ◽  
Author(s):  
B. N. Ling ◽  
C. F. Hinton ◽  
D. C. Eaton
Keyword(s):  
High Selectivity ◽  
Primary Cultures ◽  
Principal Cell ◽  
Na Channel ◽  
Open Probability ◽  
Inward Current ◽  
Collecting Tubule ◽  
Apical Membranes ◽  
Rabbit Cortical Collecting Tubule ◽  
Cortical Collecting Tubule

Patch-clamp methodology was applied to principal cell apical membranes of rabbit cortical collecting tubule (CCT) primary cultures grown on collagen supports in the presence of aldosterone (1.5 microM). The most frequently observed channel had a unit conductance of 3-5 pS, nonlinear current-voltage (I-V) relationship, Na permeability (PNa)-to-K permeability (PK) ratio greater than 19:1, and inward current at all applied potentials (Vapp) less than +80 mV (n = 41). Less frequently, an 8- to 10-pS channel with a linear I-V curve, PNa/PK less than 5:1, and inward current at Vapp less than +40 mV was also observed (n = 7). Luminal amiloride (0.75 microM) decreased the open probability (Po) for both of these channels. Mean open time for the high-selectivity Na+ channel was 2.1 +/- 0.5 s and for the low-selectivity Na+ channel was 50 +/- 12 ms. In primary cultures grown without aldosterone the high-selectivity Na+ channel was rarely observed (1 of 32 patches). Lastly, a 26- to 35-pS channel, nonselective for Na+ over K+, was not activated by cytoplasmic Ca2+ or voltage nor inhibited by amiloride (n = 17). We conclude that under specific growth conditions, namely permeable transporting supports and chronic mineralocorticoid hormone exposure, principal cell apical membranes of rabbit CCT primary cultures contain 1) both high-selectivity and low-selectivity, amiloride-inhibitable Na+ channels and 2) amiloride-insensitive, nonselective cation channels.

scholarly journals Gating of Na channels in the rat cortical collecting tubule: effects of voltage and membrane stretch.

1996 ◽  
Vol 107 (1) ◽  
pp. 35-45 ◽  
Author(s):  
L G Palmer ◽  
G Frindt
Keyword(s):  
Voltage Dependence ◽  
Single Channel ◽  
Apical Membrane ◽  
Na Channels ◽  
Patch Clamp Technique ◽  
Open Time ◽  
Collecting Tubule ◽  
Excised Patches ◽  
The Mean ◽  
Cortical Collecting Tubule

The gating kinetics of apical membrane Na channels in the rat cortical collecting tubule were assessed in cell-attached and inside-out excised patches from split-open tubules using the patch-clamp technique. In patches containing a single channel the open probability (Po) was variable, ranging from 0.05 to 0.9. The average Po was 0.5. However, the individual values were not distributed normally, but were mainly < or = 0.25 or > or = 0.75. Mean open times and mean closed times were correlated directly and inversely, respectively, with Po. In patches where a sufficient number of events could be recorded, two time constants were required to describe the open-time and closed-time distributions. In most patches in which basal Po was < 0.3 the channels could be activated by hyperpolarization of the apical membrane. In five such patches containing a single channel hyperpolarization by 40 mV increased Po by 10-fold, from 0.055 +/- 0.023 to 0.58 +/- 0.07. This change reflected an increase in the mean open time of the channels from 52 +/- 17 to 494 +/- 175 ms and a decrease in the mean closed time from 1,940 +/- 350 to 336 +/- 100 ms. These responses, however, could not be described by a simple voltage dependence of the opening and closing rates. In many cases significant delays in both the activation by hyperpolarization and deactivation by depolarization were observed. These delays ranged from several seconds to several tens of seconds. Similar effects of voltage were seen in cell-attached and excised patches, arguing against a voltage-dependent chemical modification of the channel, such as a phosphorylation. Rather, the channels appeared to switch between gating modes. These switches could be spontaneous but were strongly influenced by changes in membrane voltage. Voltage dependence of channel gating was also observed under whole-cell clamp conditions. To see if mechanical perturbations could also influence channel kinetics or gating mode, negative pressures of 10-60 mm Hg were applied to the patch pipette. In most cases (15 out of 22), this maneuver had no significant effect on channel behavior. In 6 out of 22 patches, however, there was a rapid and reversible increase in Po when the pressure was applied. In one patch, there was a reversible decrease. While no consistent effects of pressure could be documented, membrane deformation could contribute to the variation in Po under some conditions.

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