Dual action of aldosterone on toad bladder: Na+ permeability and Na+ pump modulation

1984 ◽  
Vol 246 (4) ◽  
pp. F517-F525 ◽  
Author(s):  
C. S. Park ◽  
I. S. Edelman
Keyword(s):  
Urinary Bladder ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Electrical Conductance ◽  
Na Channel ◽  
Metabolic State ◽  
Na Pump ◽  
Na Permeability ◽  
Basolateral Side ◽  
Dual Action

The effects of aldosterone on the functional characteristics of the Na+ entry step across the apical membrane and on the Na+ exit step across the basolateral membrane of the urinary bladder of toads were examined using amiloride and ouabain as probes of the respective surfaces of the cell. Aldosterone stimulated Na+ transport with a concurrent increase in the transepithelial electrical conductance as did two other agents, vasopressin (ADH) and p-chloromercuriphenylsulfonate (PCMPS), primarily active on the apical membrane. Unlike the effects of ADH and PCMPS, however, the effect of aldosterone on Na+ conductance was blocked by actinomycin D and was associated with a decreased sensitivity of the apical Na+ channel to amiloride. In addition, aldosterone increased the sensitivity of the Na+ pump on the basolateral side to ouabain, an effect that was dependent on the metabolic state of the urinary bladder. These results support the inference of coordinate effects on Na+ permeability of the apical membrane and the Na+ pump of the basolateral membrane. Both effects of aldosterone appear to be dependent on the metabolic state of the transporting epithelium.

Stimulation of apical Na permeability and basolateral Na pump of toad urinary bladder by aldosterone

1986 ◽  
Vol 250 (2) ◽  
pp. F273-F281
Author(s):  
L. G. Palmer ◽  
N. Speez
Keyword(s):  
Urinary Bladder ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Apical Cell ◽  
Toad Urinary Bladder ◽  
Apical Cell Membrane ◽  
Na Pump ◽  
Na Permeability ◽  
Pump Rate ◽  
Stimulation Of

The effect of aldosterone on Na entry and Na exit from the toad urinary bladder epithelium was studied using current-voltage analysis of the apical cell membrane to measure apical Na permeability (PNa) and the intracellular Na activity (Nac). Varying the activity of Na in the mucosal solution elicited parallel changes in active Na transport (INa) and Nac, allowing the activation of the basolateral Na pump by Nac to be evaluated. Five hours after addition of aldosterone, INa increased 130% and PNa increased 140% relative to controls. The pump rate at an arbitrarily chosen value of Nac = 4 mM [Ip(4)] increased 53%. Eighteen hours after addition of the hormone, INa increased 500%, PNa increased 680%, and Ip(4) increased 110%. ADH increased INa and PNa without changing Ip(4), whereas KCN decreased all three parameters. A change in the activation curve for the pump induced by aldosterone was also observed in the presence of mucosal nystatin, which permeabilized the apical membrane, allowing Nac to be controlled. Attempts to distinguish an effect on the maximal pump rate from one on the affinity for Na were equivocal. The results imply that aldosterone has independent stimulatory effects on Na entry across the apical membrane and Na exit across the basolateral membrane but that the stimulation of the entry process is considerably stronger.

EGF and PGE2 inhibit rabbit CCD Na+ transport by different mechanisms: PGE2 inhibits Na(+)-K+ pump

1993 ◽  
Vol 264 (4) ◽  
pp. F670-F677 ◽  
Author(s):  
D. H. Warden ◽  
J. B. Stokes
Keyword(s):  
Apical Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Membrane Conductance ◽  
Membrane Voltage ◽  
Na Channel ◽  
Cortical Collecting Duct ◽  
Na Transport ◽  
Flux Measurements ◽  
Epidermal Growth

The rabbit cortical collecting duct absorbs Na+ by a transport system comprised of an apical membrane Na+ channel and a basolateral membrane Na(+)-K(+)-adenosinetriphosphatase. The rate of Na+ absorption across this epithelium is acutely inhibited by several hormones and autacoids including epidermal growth factor (EGF) and prostaglandin E2 (PGE2). We used electrophysiological analysis to determine which Na+ transport mechanism is primarily regulated in response to EGF and PGE2. We used concentrations of EGF and PGE2 that inhibited Na+ absorption to a comparable degree. We assessed the effects of these agents on Na+ transport primarily by the calculated equivalent current; the validity of this indicator was verified using simultaneous tracer flux measurements. EGF and PGE2 had different effects on the intracellular electrophysiological parameters. EGF (in the presence of a cyclooxygenase inhibitor) hyperpolarized the apical membrane voltage in a manner analogous to the Na(+)-channel blocker amiloride, reduced the transepithelial conductance, and increased the fractional resistance of the apical membrane. In comparison, PGE2 depolarized the apical membrane voltage in a manner analogous to the Na(+)-K+ pump inhibitor ouabain, and caused no significant changes in transepithelial conductance or apical membrane conductance. The finding that EGF hyperpolarized the apical membrane indicates that this agent attenuates Na+ absorption by reducing apical Na+ entry due to a decrease in the magnitude of the apical membrane Na+ conductance. In contrast, the electrophysiological changes produced by PGE2 indicate primary inhibition of the basolateral Na(+)-K+ pump following PGE2 treatment.

scholarly journals Anion-sensitive sodium conductance in the apical membrane of toad urinary bladder.

1980 ◽  
Vol 76 (1) ◽  
pp. 69-81 ◽  
Author(s):  
J Narvarte ◽  
A L Finn
Keyword(s):  
Membrane Potential ◽  
Urinary Bladder ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Potentials ◽  
Toad Urinary Bladder ◽  
Bladder Epithelium ◽  
Anionic Composition ◽  
Before And After ◽  
Cl Conductance

Membrane potentials and the electrical resistance of the cell membranes and the shunt pathway of toad urinary bladder epithelium were measured using microelectrode techniques. These measurements were used to compute the equivalent electromotive forces (EMF) at both cell borders before and after reductions in mucosal Cl- concentration ([Cl]m). The effects of reduction in [Cl]m depended on the anionic substitute. Gluconate or sulfate substitutions increased transepithelial resistance, depolarized membrane potentials and EMF at both cell borders, and decreased cell conductance. Iodide substitutions had opposite effects. Gluconate or sulfate substitutions decreased apical Na conductance, where iodide replacements increased it. When gluconate or sulfate substitutions were brought about the presence of amiloride in the mucosal solution, apical membrane potential and EMF hyperpolarized with no significant changes in basolateral membrane potential or EMF. It is concluded that: (a) apical Na conductance depends, in part, on the anionic composition of the mucosal solution, (b) there is a Cl- conductance in the apical membrane, and (c) the electrical communication between apical and basolateral membranes previously described is mediated by changes in the size of the cell Na pool, most likely by a change in sodium activity.

scholarly journals A Chloride Channel at the Basolateral Membrane of the Distal-convoluted Tubule

2003 ◽  
Vol 121 (4) ◽  
pp. 287-300 ◽  
Author(s):  
Stéphane Lourdel ◽  
Marc Paulais ◽  
Pedro Marvao ◽  
Antoine Nissant ◽  
Jacques Teulon
Keyword(s):  
Patch Clamp ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Distal Convoluted Tubule ◽  
Patch Clamp Technique ◽  
Anion Selectivity ◽  
Basolateral Side ◽  
Cl Channels ◽  
Inside Out ◽  
External Calcium

The distal-convoluted tubule (DCT) of the kidney absorbs NaCl mainly via an Na+-Cl− cotransporter located at the apical membrane, and Na+, K+ ATPase at the basolateral side. Cl− transport across the basolateral membrane is thought to be conductive, but the corresponding channels have not yet been characterized. In the present study, we investigated Cl− channels on microdissected mouse DCTs using the patch-clamp technique. A channel of ∼9 pS was found in 50% of cell-attached patches showing anionic selectivity. The NPo in cell-attached patches was not modified when tubules were preincubated in the presence of 10−5 M forskolin, but the channel was inhibited by phorbol ester (10−6 M). In addition, NPo was significantly elevated when the calcium in the pipette was increased from 0 to 5 mM (NPo increased threefold), or pH increased from 6.4 to 8.0 (NPo increased 15-fold). Selectivity experiments conducted on inside-out patches showed that the Na+ to Cl− relative permeability was 0.09, and the anion selectivity sequence Cl− ∼ I−> Br− ∼ NO3− > F−. Intracellular NPPB (10−4 M) and DPC (10−3 M) blocked the channel by 65% and 80%, respectively. The channel was inhibited at acid intracellular pH, but intracellular ATP and PKA had no effect. ClC-K Cl− channels are characterized by their sensitivity to the external calcium and to pH. Since immunohistochemical data indicates that ClC-K2, and perhaps ClC-K1, are present on the DCT basolateral membrane, we suggest that the channel detected in this study may belong to this subfamily of the ClC channel family.

Na+ transport in isolated rat CCD: effects of bradykinin, ANP, clonidine, and hydrochlorothiazide

1991 ◽  
Vol 260 (1) ◽  
pp. F86-F95 ◽  
Author(s):  
A. J. Rouch ◽  
L. Chen ◽  
S. L. Troutman ◽  
J. A. Schafer
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Potential Difference ◽  
Na Channel ◽  
Bathing Solution ◽  
Channel Blockers ◽  
Na Transport ◽  
Luminal Membrane ◽  
Collecting Ducts ◽  
Basolateral Membrane Potential

We examined the effects of bradykinin (BK), atrial natriuretic peptide (ANP), hydrochlorothiazide (HCTZ), and clonidine on Na+ transport in isolated perfused cortical collecting ducts from rats treated with deoxycorticosterone. Arginine vasopressin was present in the bathing solution at 220 pM. Clonidine (1 microM, bathing solution) depolarized transepithelial potential difference (PDT) from -11.9 +/- 2.0 (SE) to -7.4 +/- 1.7 mV (P less than 0.001), hyperpolarized basolateral membrane potential difference (PDbl) from -85 +/- 1 to -87 +/- 1 mV (P less than 0.01), and increased the fractional resistance of the apical membrane (FRa) from 0.81 +/- 0.02 to 0.86 +/- 0.02 (P less than 0.03), indicating that it inhibited the Na+ conductance of the luminal membrane. BK (1 or 10 nM) or ANP (10 nM) in the bathing solution had no effect on PDT, PDbl, or FRa. BK, ANP, or 0.1 mM luminal HCTZ also had no effect on lumen-to-bath 22Na+ flux (J1----b), whereas we showed previously that clonidine inhibits J1----b by 30% (L. Chen, M. Paris, S. K. Williams, M. C. Reif, and J. A. Schafer. Kidney Int. 37: 366, 1990). Luminal addition of Na+ channel blockers amiloride (10 microM) or benzamil (1 microM) reduced J1----b to a level not significantly different from bath-to-lumen 22Na+ flux measured previously (M. Reif, S. L. Troutman, and J. A. Schafer. J. Clin. Invest. 77: 1291-1298, 1986), and neither BK nor HCTZ had any further effect. These results show that transcellular Na+ transport occurs exclusively through the apical membrane amiloride-sensitive channel, and this conductance is inhibited by clonidine but not by BK, ANP, or HCTZ.

Electrophysiology and noise analysis of K+-depolarized epithelia of frog skin

1985 ◽  
Vol 249 (5) ◽  
pp. C421-C429 ◽  
Author(s):  
J. Tang ◽  
F. J. Abramcheck ◽  
W. Van Driessche ◽  
S. I. Helman
Keyword(s):  
Frog Skin ◽  
Single Channel ◽  
Apical Membrane ◽  
Short Circuit ◽  
Noise Analysis ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Membrane Resistance ◽  
Na Channel ◽  
Channel Density

Epithelia of frog skin bathed either symmetrically with a sulfate-Ringer solution or bathed asymmetrically and depolarized with a 112 mM K+ basolateral solution (Kb+) were studied with intracellular microelectrode techniques. Kb+ depolarization caused an initial decrease of the short-circuit current (Isc) with a subsequent return of the Isc toward control values in 60-90 min. Whereas basolateral membrane resistance (Rb) and voltage were decreased markedly by high [Kb+], apical membrane electrical resistance (Ra) was decreased also. After 60 min, intracellular voltage averaged -27.3 mV, transcellular fractional resistance (fRa) was 86.8%, and Ra and Rb were decreased to 36.1 and 13.0%, of their control values, respectively. Amiloride-induced noise analysis of the apical membrane Na+ channels revealed that Na+ channel density was increased approximately 72% while single-channel Na+ current was decreased to 39.9% of control, roughly proportional to the decrease of apical membrane voltage (34.0% of control). In control and Kb+-depolarized epithelia, the Na+ channel density exhibited a phenomenon of autoregulation. Inhibition of Na+ entry (by amiloride) caused large increases of Na+ channel density toward saturating values of approximately 520 X 10(6) channels/cm2 in Kb+-depolarized tissues.

Turtle urinary bladder: regulation of ion transport by dynamic changes in plasma membrane area

1989 ◽  
Vol 257 (5) ◽  
pp. R973-R981
Author(s):  
D. L. Stetson
Keyword(s):  
Urinary Bladder ◽  
Ion Transport ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Transport Processes ◽  
Granular Cells ◽  
Membrane Area ◽  
Low Co2 ◽  
In Series ◽  
Cl Channels

Turtle urinary bladder possesses four ion transport processes: Na+ absorption, H+ secretion, and HCO3- secretion-Cl- absorption. Each transport process is performed by a specific epithelial cell type. Granular cells absorb Na+ but they are not sensitive to antidiuretic hormone (ADH), unlike toad bladder granular cells. alpha-Carbonic anhydrase-rich (CA) cells secrete H+ via an apical H+-adenosinetriphosphatase (ATPase). Under conditions of low CO2 tension, this active pump is contained in the limiting membranes of certain cytoplasmic vesicles. The vesicles fuse with the apical membrane, and H+ pumps are incorporated into that membrane, as physiological conditions demand increased H+ secretion. The stimulus for fusion of these vesicles with the apical membrane appears to be intracellular acidification. beta-CA cells secrete HCO3- and reabsorb Cl-, both processes driven by H+-ATPase in the basolateral membrane in series with an apical Cl- -HCO3- exchanger. Increased intracellular adenosine 3',5'-cyclic monophosphate concentration in beta-cells stimulates net HCO3- secretion and induces an electrogenic component of this flux by activating an apical Cl- channel. This activation accompanies the fusion of an intracellular tubulovesicular network with the apical membrane. The membrane of this network may contain Cl- channels.

scholarly journals Relationship of the aldosterone-induced protein, GP70, to the conductive Na+ channel.

1991 ◽  
Vol 2 (6) ◽  
pp. 1108-1114
Author(s):  
H Szerlip ◽  
P Palevsky ◽  
M Cox ◽  
B Blazer-Yost
Keyword(s):  
Urinary Bladder ◽  
Apical Membrane ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Na Channel ◽  
Toad Urinary Bladder ◽  
Apical Surface ◽  
Large Protein ◽  
Channel Modulation ◽  
Relationship Of

Although one of the primary effects of aldosterone is to increase apical membrane Na+ conductance, as yet none of the proteins induced by the hormone in renal epithelia have been shown to be related to the conductive Na+ channel. Because the toad urinary bladder aldosterone-induced glycoprotein, GP70, has recently been localized to the apical surface of this Na+ transporting epithelium, whether GP70 is associated with the Na+ channel was examined. The specificities of a monoclonal antibody used to characterize GP70 (mAb 20) and a polyclonal antibody raised against the purified bovine renal papillary Na+ channel (anti-CH) were compared: GP70 was specifically immunoprecipitated by both mAb 20 and anti-CH. Moreover, the sodium dodecyl sulfate-polyacrylamide gel electrophoresis profile of mAb 20 purified toad urinary bladder membrane preparations was similar to those reported for bovine and A6 cell Na+ channels. Under nonreducing conditions, a single, very large protein was evident; reduction yielded GP70, a 140-kd polypeptide, and a number of minor bands. Interestingly, only GP70 was induced by aldosterone. Thus, GP70 appears to be associated with the toad urinary bladder conductive Na+ channel; whether GP70 is an integral subunit of the channel or whether it functions as a regulatory moiety remains to be determined. Whatever the case, because GP70 is induced by aldosterone, it likely has a central role in Na+ channel modulation.

Characterization of an apical sodium conductance in rabbit cecum

1993 ◽  
Vol 264 (1) ◽  
pp. G13-G21 ◽  
Author(s):  
J. H. Sellin ◽  
A. Hall ◽  
E. J. Cragoe ◽  
W. P. Dubinsky
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Electrical Potential ◽  
Membrane Vesicles ◽  
Distal Colon ◽  
Inhibitory Effect ◽  
Na Channel ◽  
Ionic Conductances ◽  
Tight Epithelia

Rabbit cecum in vitro exhibits electrogenic Na+ absorption not blocked by amiloride but inhibited by the amiloride analogue phenamil, suggesting transport mediated by modified Na+ channels in the apical membrane. To further characterize the mechanism(s) of Na+ absorption, microelectrode impalements of single epithelial cells were performed to measure intracellular potential difference (psi mc) and fractional resistance of the apical membrane, to characterize ionic conductances of the apical and basolateral membranes, and to determine the response to phenamil. The electrical potential profile of cecum (psi mc = -31 +/- 2 mV, fractional resistance = 0.71 +/- 0.03) was qualitatively similar to distal colon. The apical membrane exhibited responses suggesting both Na+ and K+ conductances, whereas the basolateral membrane appeared to have a predominant K+ conductance. Phenamil elicited a depolarization of psi mc and a decrease in fractional resistance; neither response is consistent with inhibition of an apical Na+ conductance. Studies were performed in apical membrane vesicles to characterize ionic conductances by a second independent methodology. These additional studies confirmed the presence of an apical Na+ conductance not inhibited by either amiloride or phenamil. Thus both microelectrode impalement and vesicle studies demonstrated an apical membrane Na+ conductance in rabbit cecum; this is the likely mechanism of electrogenic Na+ absorption in this epithelium. However, the anomalous response to phenamil suggests that the inhibitory effect of this agent is not directly on the conductance. The cecal transporter may be one of a family of cation channels related to, but significantly different from, the classic Na+ channel found in distal colon and other tight epithelia.

scholarly journals Sodium transport effects on the basolateral membrane in toad urinary bladder.

1982 ◽  
Vol 80 (5) ◽  
pp. 733-751 ◽  
Author(s):  
C W Davis ◽  
A L Finn
Keyword(s):  
Urinary Bladder ◽  
Time Course ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Resistance ◽  
Membrane Voltage ◽  
Toad Urinary Bladder ◽  
Na Transport ◽  
Bladder Epithelium ◽  
Current Output

In toad urinary bladder epithelium, inhibition of Na transport with amiloride causes a decrease in the apical (Vmc) and basolateral (Vcs) membrane potentials. In addition to increasing apical membrane resistance (Ra), amiloride also causes an increase in basolateral membrane resistance (Rb), with a time course such that Ra/Rb does not change for 1-2 min. At longer times after amiloride (3-4 min), Ra/Rb rises from its control values to its amiloride steady state values through a secondary decrease in Rb. Analysis of an equivalent electrical circuit of the epithelium shows that the depolarization of Vcs is due to a decrease in basolateral electromotive force (Vb). To see of the changes in Vcs and Rb are correlated with a decrease in Na transport, external current (Ie) was used to clamp Vmc to zero, and the effects of amiloride on the portion of Ie that takes the transcellular pathway were determined. In these studies, Vcs also depolarized, which suggests that the decrease in Vb was due to a decrease in the current output of a rheogenic Na pump. Thus, the basolateral membrane does not behave like an ohmic resistor. In contrast, when transport is inhibited during basolateral membrane voltage clamping, the apical membrane voltage changes are those predicted for a simple, passive (i.e., ohmic) element.

Sign in / Sign up

Export Citation Format

Share Document