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 Microelectrode studies in toad urinary bladder epithelium. effects of Na concentration changes in the mucosal solution on equivalent electromotive forces.

1980 ◽  
Vol 75 (3) ◽  
pp. 323-344 ◽  
Author(s):  
J Narvarte ◽  
A L Finn
Keyword(s):  
Urinary Bladder ◽  
Direct Relationship ◽  
Apical Membrane ◽  
Sodium Concentration ◽  
Toad Urinary Bladder ◽  
Base Line ◽  
Bladder Epithelium ◽  
Before And After ◽  
Concentration Changes ◽  
Toad Urinary Bladder Epithelium

Microelectrode techniques were employed to measure membrane potentials, the electrical resistance of the cell membranes, and the shunt pathway, and to compute the equivalent electromotive forces (EMF) at both cell borders in toad urinary bladder epithelium before and after reductions in mucosal sodium concentration. Basal electrical parameters were not significantly different from those obtained with impalements from the serosal side, indicating that mucosal impalements do not produce significant leaks in the apical membrane. A decrease in mucosal Na concentration caused the cellular resistance to increase and both apical and basolateral EMF to depolarize. When Na was reduced from 112 to 2.4 mM in bladders with spontaneously different baseline values of transepithelial potential difference (Vms), a direct relationship was found between the change in Vms brought about by the Na reduction and the base-line Vms before the change. A direct relationship was also found by plotting the change in EMF at the apical or basolateral border caused by a mucosal Na reduction with the corresponding base-line EMF before the change. These results indicate that resting apical membrane EMF (and, therefore, resting apical membrane potential) is determined by the Na selectivity of the apical membrane, whereas basolateral EMF is at least in part the result of rheogenic Na transport. These results are consistent with data of others that suggested a link between the activity of the basolateral Na pump and apical Na conductance.

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.

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.

Stimulation by cGMP of apical Na channels and cation channels in toad urinary bladder

1991 ◽  
Vol 260 (2) ◽  
pp. C234-C241 ◽  
Author(s):  
S. Das ◽  
M. Garepapaghi ◽  
L. G. Palmer
Keyword(s):  
Urinary Bladder ◽  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Toad Urinary Bladder ◽  
Na Channels ◽  
Serosal Side ◽  
Cyclic Monophosphate ◽  
Stimulation Of

The effects of 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) on apical membrane cation conductances in the toad urinary bladder were investigated. 8-BrcGMP (1 mM) added to the serosal solution increased the amiloride-sensitive short-circuit current (INa) after a delay of 5 min to a steady-state value 1.8 times that of controls achieved after 30 min. Similar effects were seen when the bladders were bathed on the serosal side with a normal NaCl Ringer solution and with a high-K sucrose solution to depolarize the basolateral membrane. Under the latter conditions, the amiloride-sensitive transepithelial conductance increased in parallel with the short-circuit current, indicating stimulation of apical membrane Na channels. The threshold concentration for observing the stimulation of INa was 100 microM, 10-100 times larger than the concentration of 8-bromoadenosine 3',5'-cyclic monophosphate (8-BrcAMP) required to elicit an increase in INa. Currents through an outwardly rectifying Ca-sensitive cation conductance (Iout) were also increased by 1.8-fold relative to controls. This stimulatory effect occurred after a delay of 15 min and reached maximal levels 90-120 min after addition of the nucleotide. The effects of cGMP on INa were not additive with those of 8-BrcAMP or with antidiuretic hormone, an agent known to act by increasing cAMP within the cell. Addition of 1 mM 3-isobutyl-1-methylxanthine to the serosal side of the bladders stimulated INa by 1.3-fold and Iout by 2.4-fold. In both cases, subsequent addition of cGMP produced no further activation of either conductance.(ABSTRACT TRUNCATED AT 250 WORDS)

Colistin interactions with the mammalian urothelium

2004 ◽  
Vol 286 (4) ◽  
pp. C913-C922 ◽  
Author(s):  
Jamie R. Lewis ◽  
Simon A. Lewis
Keyword(s):  
Membrane Potential ◽  
Urinary Bladder ◽  
Binding Site ◽  
Apical Membrane ◽  
Divalent Cations ◽  
Membrane Binding ◽  
Short Exposure ◽  
Cell Interior ◽  
Bladder Epithelium ◽  
Conductance Increase

Here we describe the effect of colistin on the barrier function of the mammalian urinary bladder epithelium. Addition of colistin to the mucosal solution of the rabbit urinary bladder epithelium (urothelium) resulted in an increase in the transepithelial conductance. The magnitude of the increase in transepithelial conductance was dependent on the membrane voltage, concentration of colistin, and presence of divalent cations in the bath solution. The initial site of action of colistin was at the apical membrane. Colistin increased the membrane conductance only when the apical membrane potential was cell interior negative. The more negative the membrane potential, the larger the conductance increase. The concentration dependence of the conductance increase saturated, suggesting a membrane binding site. Divalent cations decreased the magnitude of the conductance increase. This divalent cation action occurred at two sites: one in competition with colistin for a membrane binding site, and the other by rapidly blocking the induced conductance. At short exposure times, the increase in conductance was reversed by either removing colistin from the bath or changing the voltage so that the apical membrane was cell interior positive. At long exposure times, the increase was only partially reversible by voltage or removal from the bath. This finding suggests that at long exposure times, there is a toxic effect of colistin on the urothelium.

Role of PKC isozymes in water transport in toad urinary bladder

1991 ◽  
Vol 49 ◽  
pp. 302-303
Author(s):  
A.J. Mia ◽  
L.X. Oakford ◽  
T. Yorio
Keyword(s):  
Urinary Bladder ◽  
Apical Membrane ◽  
Membrane Surface ◽  
Protein A ◽  
Cell Types ◽  
Leukemic Cells ◽  
Toad Urinary Bladder ◽  
Pkc Isozymes ◽  
Antibody Labeling

Protein kinase C (PKC) isozymes, when activated, are translocated to particulate membrane fractions for transport to the apical membrane surface in a variety of cell types. Evidence of PKC translocation was demonstrated in human megakaryoblastic leukemic cells, and in cardiac myocytes and fibroblasts, using FTTC immunofluorescent antibody labeling techniques. Recently, we reported immunogold localizations of PKC subtypes I and II in toad urinary bladder epithelia, following 60 min stimulation with Mezerein (MZ), a PKC activator, or antidiuretic hormone (ADH). Localization of isozyme subtypes I and n was carried out in separate grids using specific monoclonal antibodies with subsequent labeling with 20nm protein A-gold probes. Each PKC subtype was found to be distributed singularly and in discrete isolated patches in the cytosol as well as in the apical membrane domains. To determine if the PKC isozymes co-localized within the cell, a double immunogold labeling technique using single grids was utilized.

scholarly journals Electrophysiological effects of basolateral [Na+] in Necturus gallbladder epithelium.

1992 ◽  
Vol 99 (2) ◽  
pp. 241-262 ◽  
Author(s):  
G A Altenberg ◽  
J S Stoddard ◽  
L Reuss
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Resistance ◽  
Membrane Voltage ◽  
Gallbladder Epithelium ◽  
K Channels ◽  
Necturus Gallbladder ◽  
Electrophysiological Effects ◽  
Paracellular Diffusion ◽  
Cl Conductance

In Necturus gallbladder epithelium, lowering serosal [Na+] ([Na+]s) reversibly hyperpolarized the basolateral cell membrane voltage (Vcs) and reduced the fractional resistance of the apical membrane (fRa). Previous results have suggested that there is no sizable basolateral Na+ conductance and that there are apical Ca(2+)-activated K+ channels. Here, we studied the mechanisms of the electrophysiological effects of lowering [Na+]s, in particular the possibility that an elevation in intracellular free [Ca2+] hyperpolarizes Vcs by increasing gK+. When [Na+]s was reduced from 100.5 to 10.5 mM (tetramethylammonium substitution), Vcs hyperpolarized from -68 +/- 2 to a peak value of -82 +/- 2 mV (P less than 0.001), and fRa decreased from 0.84 +/- 0.02 to 0.62 +/- 0.02 (P less than 0.001). Addition of 5 mM tetraethylammonium (TEA+) to the mucosal solution reduced both the hyperpolarization of Vcs and the change in fRa, whereas serosal addition of TEA+ had no effect. Ouabain (10(-4) M, serosal side) produced a small depolarization of Vcs and reduced the hyperpolarization upon lowering [Na+]s, without affecting the decrease in fRa. The effects of mucosal TEA+ and serosal ouabain were additive. Neither amiloride (10(-5) or 10(-3) M) nor tetrodotoxin (10(-6) M) had any effects on Vcs or fRa or on their responses to lowering [Na+]s, suggesting that basolateral Na+ channels do not contribute to the control membrane voltage or to the hyperpolarization upon lowering [Na+]s. The basolateral membrane depolarization upon elevating [K+]s was increased transiently during the hyperpolarization of Vcs upon lowering [Na+]s. Since cable analysis experiments show that basolateral membrane resistance increased, a decrease in basolateral Cl- conductance (gCl-) is the main cause of the increased K+ selectivity. Lowering [Na+]s increases intracellular free [Ca2+], which may be responsible for the increase in the apical membrane TEA(+)-sensitive gK+. We conclude that the decrease in fRa by lowering [Na+]s is mainly caused by an increase in intracellular free [Ca2+], which activates TEA(+)-sensitive maxi K+ channels at the apical membrane and decreases apical membrane resistance. The hyperpolarization of Vcs is due to increase in: (a) apical membrane gK+, (b) the contribution of the Na+ pump to Vcs, (c) basolateral membrane K+ selectivity (decreased gCl-), and (d) intraepithelial current flow brought about by a paracellular diffusion potential.

Activation of CFTR Cl- conductance in polarized T84 cells by luminal extracellular ATP

1995 ◽  
Vol 268 (2) ◽  
pp. C425-C433 ◽  
Author(s):  
M. J. Stutts ◽  
E. R. Lazarowski ◽  
A. M. Paradiso ◽  
R. C. Boucher
Keyword(s):  
Adenosine Receptor ◽  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Apical Cell ◽  
Extracellular Atp ◽  
T84 Cells ◽  
Apical Cell Membrane ◽  
Cl Secretion ◽  
Cl Conductance

Luminal extracellular ATP evoked a bumetanide-sensitive short-circuit current in cultured T84 cell epithelia (90.2 +/- 18.2 microA/cm2 at 100 microM ATP, apparent 50% effective concentration, 11.5 microM). ATP appeared to increase the Cl- conductance of the apical membrane but not the driving force for Cl- secretion determined by basolateral membrane K+ conductance. Specifically, the magnitude of Cl- secretion stimulated by ATP was independent of basal current, and forskolin pretreatment abolished subsequent stimulation of Cl- secretion by ATP. Whereas ATP stimulated modest production of adenosine 3',5'-cyclic monophosphate (cAMP) by T84 cells, ATP caused smaller increases in intracellular Ca2+ and inositol phosphate activities than the Ca(2+)-signaling Cl- secretagogue carbachol. An inhibitor of 5'-nucleotidase, alpha,beta-methyleneadenosine 5'-diphosphate, blocked most of the response to luminal ATP. The adenosine receptor antagonist 8-(p-sulfophenyl)theophylline blocked both the luminal ATP-dependent generation of cAMP and Cl- secretion when administered to the luminal but not submucosal bath. These results demonstrate that the Cl- secretion stimulated by luminal ATP is mediated by a A2-adenosine receptor located on the apical cell membrane. Thus metabolism of extracellular ATP to adenosine regulates the activity of cystic fibrosis transmembrane conductor regulator (CFTR) in the apical membrane of polarized T84 cells.

Electrophysiological evidence for Cl secretion in shark renal proximal tubules

1985 ◽  
Vol 248 (2) ◽  
pp. F282-F295 ◽  
Author(s):  
K. W. Beyenbach ◽  
E. Fromter
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Proximal Tubules ◽  
In Vitro Perfusion ◽  
Electrophysiological Properties ◽  
Electrophysiological Responses ◽  
Tubule Lumen ◽  
Transepithelial Voltage ◽  
Cl Conductance

The electrophysiology of shark proximal tubules (Squalus acanthias) was investigated using conventional microelectrodes and cable analysis. Under in vitro perfusion with symmetrical Ringer solutions, tubule transepithelial resistance was 36.3 +/- 2.3 omega X cm2 (means +/- SE, n = 44). Other electrophysiological variables varied widely under control conditions. In unstimulated tubules (n = 16) the transepithelial voltage (VT,o) was lumen positive (1.2 +/- 0.2 mV), the basolateral membrane potential (Vbl,x) was -61.3 +/- 1.6 mV, and the fractional resistance of the apical membrane (fRa) was 0.67 +/- 0.02. Spontaneously stimulated tubules (n = 28) had lumen-negative VT,o values (-1.5 +/- 0.4 mV), low Vbl,x values (-41.3 +/- 1.7 mV), and low fRa values (0.30 +/- 0.02). The stimulated state can be induced in unstimulated tubules via treatment with cAMP. Multiple microelectrode impalements in a single tubule revealed epithelial cells sharing similar electrophysiological properties. Selective ion substitutions in the tubule lumen and peritubular bath uncovered an increased Cl conductance in the apical membrane of spontaneously and cAMP-stimulated tubules. Anthracene-9-carboxylic acid tended to reverse the stimulated state, and furosemide hyperpolarized Vbl,x. These results constitute the first evidence for secretory Cl transport in a renal proximal tubule. The electrophysiological responses to ion substitutions, stimulators, and inhibitors are strikingly similar to those of known Cl-transporting epithelia.

Sign in / Sign up

Export Citation Format

Share Document