scholarly journals Effects of ouabain on fluid transport and electrical properties of Necturus gallbladder. Evidence in favor of a neutral basolateral sodium transport mechanism.

1979 ◽  
Vol 73 (4) ◽  
pp. 385-402 ◽  
Author(s):  
L Reuss ◽  
E Bello-Reuss ◽  
T P Grady
Keyword(s):  
Electrical Properties ◽  
Cell Membranes ◽  
Fluid Transport ◽  
Prolonged Exposure ◽  
Basolateral Membrane ◽  
Bathing Solution ◽  
Na Transport ◽  
Bathing Medium ◽  
Necturus Gallbladder ◽  
Before And After

Net fluid transport (Jv) and electrical properties of the cell membranes and paracellular pathway of Necturus gallbladder epithelium were studied before and after the addition of ouabain (10(-4) M) to the serosal bathing medium. The glycoside inhibited Jv by 70% in 15 min and by 100% in 30 min. In contrast, the potentials across both cell membranes did not decrease significantly until 20 min of exposure to ouabain. At 30 min, the basolateral membrane potential (Vcs) fell only by ca 7 mV. If basolateral Na transport were electrogenic, with a coupling ratio (Na:K) of 3:2, the reductions of Vcs at 15 and 30 min should be 12--15 and 17--21 mV, respectively. Thus, we conclude that the mechanism of Na transport from the cells to the serosal bathing solution is not electrogenic under normal transport conditions. The slow depolarization observed in ouabain is caused by a fall of intracellular K concentration, and by a decrease in basolateral cell membrane K permeability. Prolonged exposure to ouabain results also in an increase in paracellular K selectivity, with no change of P Na/P Cl.

Potassium-induced cell swelling in Necturus gallbladder epithelium

1988 ◽  
Vol 254 (5) ◽  
pp. C643-C650 ◽  
Author(s):  
C. W. Davis ◽  
A. L. Finn
Keyword(s):  
Cell Volume ◽  
Volume Regulation ◽  
Basolateral Membrane ◽  
Cell Volume Regulation ◽  
Cell Swelling ◽  
Gallbladder Epithelium ◽  
Bathing Medium ◽  
Necturus Gallbladder ◽  
Per Se ◽  
Cl Conductance

In Necturus gallbladder epithelium, elevation of mucosal K+ to 95 mM in the presence of 10 mM Na+ resulted in cell swelling at a rate of 3.2% original volume per minute, followed by volume-regulatory shrinking. When Na+ was completely removed from or when amiloride (10(-4) M) was added to the mucosal medium, K+-induced cell swelling was abolished. In the presence of 10 mM Na+, 1 mM Ba2+ abolished and substitution of mucosal Cl- by NO-3 had no effect on K+-induced swelling. Thus solute entry following elevation of mucosal K+ is effected by separate K+ and Cl- pathways. Furthermore, substitution of 95 mM K+ for Na+ in the mucosal bathing medium leads to the development of a Cl- conductance in the basolateral membrane as long as some Na+ remains in the medium. However, cell swelling induced by mucosal dilution does not lead to the appearance of a Cl- conductance. Thus the activation of this conductance requires both swelling and membrane depolarization. These results show that 1) high mucosal K+ leads to cell swelling due to the entry of Cl- along with K+ and the Cl- can enter across either membrane, 2) the Cl- pathways require the presence of mucosal Na+, and 3) cell volume regulation is activated by an increase in volume per se, i.e., a hyposmotic exposure is not required for volume regulation to occur.

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.

scholarly journals Intracellular K+ activity and its relation to basolateral membrane ion transport in Necturus gallbladder epithelium.

1980 ◽  
Vol 76 (1) ◽  
pp. 33-52 ◽  
Author(s):  
L Reuss ◽  
S A Weinman ◽  
T P Grady
Keyword(s):  
Cell Membrane ◽  
Amphotericin B ◽  
Basolateral Membrane ◽  
Membrane Potentials ◽  
Equilibrium Potential ◽  
Gallbladder Epithelium ◽  
Bathing Medium ◽  
Necturus Gallbladder ◽  
Intracellular K Activity ◽  
K Activity

A study of the mechanisms of the effects of amphotericin B and ouabain on cell membrane and transepithelial potentials and intracellular K activity (alpha Ki) of Necturus gallbladder epithelium was undertaken with conventional and K-selective intracellular microelectrode techniques. Amphotericin B produced a mucosa-negative change of transepithelial potential (Vms) and depolarization of both apical and basolateral membranes. Rapid fall of alpha Ki was also observed, with the consequent reduction of the K equilibrium potential (EK) across both the apical and the basolateral membrane. It was also shown that, unless the mucosal bathing medium is rapidly exchanged, K accumulates in the unstirred fluid layers near the luminal membrane generating a paracellular K diffusion potential, which contributes to the Vms change. Exposure to ouabain resulted in a slow decrease of alpha Ki and slow depolarization of both cell membranes. Cell membrane potentials and alpha Ki could be partially restored by a brief (3-4 min) mucosal substitution of K for Na. Under all experimental conditions (control, amphotericin B, and ouabain), EK at the basolateral membrane was larger than the basolateral membrane equivalent emf (Eb). Therefore, the K chemical potential difference appears to account for Eb and the magnitude of the cell membrane potentials, without the need to postulate an electrogenic Na pump. Comparison of the rate of Na transport across the tissue with the electrodiffusional K flux across the basolateral membrane indicates that maintenance of a steady-state alpha Ki cannot be explained by a simple Na,K pump-K leak model. It is suggested that either a NaCl pump operates in parallel with the Na,K pump, or that a KCl downhill neutral extrusion mechanism exists in addition to the electrodiffusional K pathway.

Electrolyte and fluid transport across the mature alveolar epithelium

1993 ◽  
Vol 74 (1) ◽  
pp. 1-15 ◽  
Author(s):  
G. Saumon ◽  
G. Basset
Keyword(s):  
Fluid Transport ◽  
Basolateral Membrane ◽  
Adult Life ◽  
Alveolar Epithelium ◽  
Epithelial Lining ◽  
Fluid Absorption ◽  
Na Transport ◽  
Alveolar Cells ◽  
Epithelial Lining Fluid ◽  
Transepithelial Na Transport

The lungs must be kept "dry" for efficient gas exchange. The mechanisms that contribute to clear alveoli from fetal lung fluid at birth are still present during adult life and allow recovery from alveolar flooding. It has recently been shown with the use of different approaches in vitro, as well as in vivo, that alveolar epithelium performs solute-coupled fluid transport. Fluid absorption from alveoli occurs chiefly as a result of active transepithelial Na+ transport. The mechanisms of Na+ transport have been partly elucidated; Na+ enters alveolar cells through apical Na+ channels and Na(+)-coupled solute transporters and is pumped out at the basolateral membrane by a Na(+)-K(+)-adenosinetriphosphatase (ATPase). Transepithelial Na+ transport and fluid absorption are stimulated by beta-adrenergic agonists, with adenosine 3',5'-cyclic monophosphate being the likely intracellular second messenger. K+ is probably secreted into alveoli because its concentration in the epithelial lining fluid is larger than expected for passive distribution. K+ channels have been described that, in conjunction with Na(+)-K(+)-ATP-ase, might provide pathways for active transport. Active proton secretion or bicarbonate absorption have been reported, which may explain the low pH of the alveolar epithelial lining fluid. It is probable that active solute transports are the main determinants of epithelial lining fluid depth and composition. A challenge for the future is to understand how this homeostasis is achieved.

scholarly journals The Regulation of Stomatal Aperture in Tobacco Leaf Epidermal Strips

1972 ◽  
Vol 25 (5) ◽  
pp. 877 ◽  
Author(s):  
DA Thomas
Keyword(s):  
Guard Cell ◽  
Cell Membranes ◽  
Guard Cells ◽  
Stomatal Opening ◽  
Stomatal Aperture ◽  
Bathing Solution ◽  
Bathing Medium ◽  
Tobacco Leaf ◽  
Phosphoenol Pyruvate

Stepwise decreases in the stomatal aperture of tobacco leaf epidermal strips followed stepwise increases in the concentration of KHCOa added to bathing solutions. Removal of KHCOa from the bathing solution resulted in a rapid increase in aperture. The reduction in aperture caused by KHCO., both in the light and dark, can be reversed by the addition of ATP or phosphoenol pyruvate to the bathing solution. The stomatal opening, supported by a NaCl bathing medium, is reduced by the addition of NaHCOa? From the results it is suggested that HCO;/C02t increases the permeability of guard cell membranes causing a net efflux of water or ions or both from the guard cells.

Role of basolateral carbonic anhydrase in proximal tubular fluid and bicarbonate absorption

2001 ◽  
Vol 280 (1) ◽  
pp. F146-F154 ◽  
Author(s):  
Shuichi Tsuruoka ◽  
Erik R. Swenson ◽  
Snezana Petrovic ◽  
Akio Fujimura ◽  
George J. Schwartz
Keyword(s):  
Carbonic Anhydrase ◽  
Basolateral Membrane ◽  
Bathing Solution ◽  
Fluid Absorption ◽  
Cell Ph ◽  
Before And After ◽  
Proximal Tubular ◽  
Membrane Bound

Membrane-bound carbonic anhydrase (CA) is critical to renal acidification. The role of CA activity on the basolateral membrane of the proximal tubule has not been defined clearly. To investigate this issue in microperfused rabbit proximal straight tubules in vitro, we measured fluid and HCO3 −absorption and cell pH before and after the extracellular CA inhibitor p-fluorobenzyl-aminobenzolamide was applied in the bath to inhibit only basolateral CA. This inhibitor was 1% as permeant as acetazolamide. Neutral dextran (2 g/dl, molecular mass 70,000) was used as a colloid to support fluid absorption because albumin could affect CO2 diffusion and rheogenic HCO3 − efflux. Indeed, dextran in the bath stimulated fluid absorption by 55% over albumin. Basolateral CA inhibition reduced fluid absorption (∼30%) and markedly decreased HCO3 − absorption (∼60%), both reversible when CA was added to the bathing solution. In the presence of luminal CA inhibition, which reduced fluid (∼16%) and HCO3 − (∼66%) absorption, inhibition of basolateral CA further decreased the absorption of fluid (to 74% of baseline) and HCO3 − (to 22% of baseline). CA inhibition also alkalinized cell pH by ∼0.2 units, suggesting the presence of an alkaline disequilibrium pH in the interspace, which would secondarily block HCO3 − exit from the cell and thereby decrease luminal proton secretion (HCO3 −absorption). These data clearly indicate that basolateral CA has an important role in mediating fluid and especially HCO3 −absorption in the proximal straight tubule.

scholarly journals Cyclic AMP inhibits Cl-/HCO3- exchange at the apical membrane of Necturus gallbladder epithelium.

1987 ◽  
Vol 90 (2) ◽  
pp. 173-196 ◽  
Author(s):  
L Reuss
Keyword(s):  
Cyclic Amp ◽  
Apical Membrane ◽  
Phosphodiesterase Inhibitor ◽  
Intracellular Camp ◽  
Bathing Solution ◽  
Gallbladder Epithelium ◽  
Bathing Medium ◽  
Necturus Gallbladder ◽  
Mechanism Of Inhibition ◽  
Camp Levels

Intracellular microelectrode techniques were employed to study the effect of cyclic AMP on apical membrane Cl-/HCO3- exchange and electrodiffusive HCO3- transport in Necturus gallbladder epithelium. Intracellular cAMP levels were raised by addition of either the phosphodiesterase inhibitor theophylline (3 X 10(-3) M) or the adenylate cyclase activator forskolin (10(-5) M) to the serosal bathing solution. Measurements of pH in a poorly buffered control mucosal solution upon stopping superfusion show acidification, owing to secretion of both H+ and HCO3-. When the same experiment is performed after addition of amiloride or removal of Na+ from the mucosal bathing medium, alkalinization is observed since H+ transport is either inhibited or reversed, whereas HCO3- secretion persists. The changes in pH in both amiloride or Na-free medium were significantly decreased in theophylline-treated tissues. Theophylline had no effect on the initial rates of fall of intracellular Cl- activity (aCli) upon reducing mucosal solution [Cl-] to either 10 or 0 mM, although membrane voltage and resistance measurements were consistent with stimulation of apical membrane electrodiffusive Cl- permeability. Estimates of the conductive flux, obtained by either reducing simultaneously mucosal [Cl-] and [HCO3-] or lowering [Cl-] alone in the presence of a blocker of anion exchange (diphenylamine-2-carboxylate), indicate that elevation of intracellular cAMP inhibited the anion exchanger by approximately 50%. Measurements of net Cl- uptake upon increasing mucosal Cl- from nominally zero to levels ranging from 2.5 to 100 mM suggest that the mechanism of inhibition is a decrease in Vmax. Consistent with these results, the rate of intracellular alkalinization upon reducing external Cl- was also inhibited significantly by theophylline. Reducing mucosal solution [HCO3-] from 10 to 1 mM under control conditions caused intracellular acidification and an increase in aCli. Theophylline inhibited both changes, by 62 and 32%, respectively. These data indicate that elevation of intracellular cAMP inhibits apical membrane anion (Cl-/HCO3-) exchange. Studies of the effects of rapid changes in mucosal [HCO3-] on membrane voltages and the apparent ratio of membrane resistances, both in the presence and in the absence of theophylline, with or without Cl- in the mucosal solution, do not support the hypothesis that cAMP produces a sizable increase in apical membrane electrodiffusive HCO3- permeability.

scholarly journals Electrophysiological effects of extracellular ATP on Necturus gallbladder epithelium.

1991 ◽  
Vol 97 (5) ◽  
pp. 949-971 ◽  
Author(s):  
C U Cotton ◽  
L Reuss
Keyword(s):  
Cell Membrane ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Active Agent ◽  
Membrane Conductance ◽  
Membrane Resistance ◽  
Initial Increase ◽  
Bathing Solution ◽  
Gallbladder Epithelium ◽  
Necturus Gallbladder

The effects of addition of ATP to the mucosal bathing solution on transepithelial, apical, and basolateral membrane voltages and resistances in Necturus gallbladder epithelium were determined. Mucosal ATP (100 microM) caused a rapid hyperpolarization of both apical (Vmc) and basolateral (Vcs) cell membrane voltages (delta Vm = 18 +/- 1 mV), a fall in transepithelial resistance (Rt) from 142 +/- 8 to 122 +/- 7 omega.cm2, and a decrease in fractional apical membrane resistance (fRa) from 0.93 +/- 0.02 to 0.83 +/- 0.03. The rapid initial hyperpolarization of Vmc and Vcs was followed by a slower depolarization of cell membrane voltages and a lumen-negative change in transepithelial voltage (Vms). This phase also included an additional decrease in fRa. Removal of the ATP caused a further depolarization of membrane voltages followed by a hyperpolarization and then a return to control values. fRa fell to a minimum after removal of ATP and then returned to control values as the cell membrane voltages repolarized. Similar responses could be elicited by ADP but not by adenosine. The results of two-point cable experiments revealed that ATP induced an initial increase in cell membrane conductance followed by a decrease. Transient elevations of mucosal solution [K+] induced a larger depolarization of Vmc and Vcs during exposure to ATP than under control conditions. Reduction of mucosal solution [Cl-] induced a slow hyperpolarization of Vmc and Vcs before exposure to ATP and a rapid depolarization during exposure to ATP. We conclude that ATP4- is the active agent and that it causes a concentration-dependent increase in apical and basolateral membrane K+ permeability. In addition, an apical membrane electrodiffusive Cl- permeability is activated by ATP4-.

Electrophysiological effects of mucosal Cl- removal in Necturus gallbladder epithelium

1989 ◽  
Vol 257 (3) ◽  
pp. C568-C578 ◽  
Author(s):  
J. S. Stoddard ◽  
L. Reuss
Keyword(s):  
Cell Membrane ◽  
Cell Membranes ◽  
Equilibrium Potential ◽  
Bathing Solution ◽  
Gallbladder Epithelium ◽  
Membrane Hyperpolarization ◽  
Necturus Gallbladder ◽  
Partial Pressure Of Co2 ◽  
K Concentration ◽  
Electrophysiological Effects

The factors responsible for the cell membrane hyperpolarization elicited in Necturus gallbladder epithelium on Cl- removal from the mucosal bathing solution were evaluated with conventional and ion-sensitive microelectrode techniques. Cl- removal causes reversal of apical Cl- -HCO3- exchange, resulting in a fall in intracellular Cl- activity (aiCl) and an increase in intracellular pH (pHi). Concomitantly, the cell membranes hyperpolarize to values close to the K+ equilibrium potential (EK), aiNa falls, and aiK rises. The observed changes in membrane voltage are not attributable to a pHi-dependent increase in cell membrane K+ permeability (PK), because 1) the cell membrane resistances increased and 2) elevating solution partial pressure of CO2 (PCO2) to counterbalance the cellular alkalinization on mucosal Cl- removal caused a further hyperpolarization of the cell membranes to values greater than EK. This additional hyperpolarization was related to the activity of the Na+ pump, inasmuch as it was accompanied by an increase in aiNa and was ouabain sensitive. These results are consistent with, but do not prove, pump electrogenicity. During the period of Cl- removal from the mucosal bathing solution, the cell membrane depolarization caused by raising serosal K+ concentration was increased, whereas the depolarization caused by lowering serosal Cl- concentration was decreased, compared with substitutions under control conditions. These results indicate that mucosal Cl- removal causes a decrease in basolateral PCl, which we speculate could be due to a decrease in cell volume. We conclude that the hyperpolarization of the cell membranes on mucosal Cl- removal is primarily due to the combined effects of the fall in basolateral PCl and the increase in basolateral ECl.

Basolateral membrane properties in proximal convoluted tubules of the newborn rabbit

1983 ◽  
Vol 244 (2) ◽  
pp. F172-F177
Author(s):  
M. A. Linshaw ◽  
L. W. Welling
Keyword(s):  
Cell Membranes ◽  
Basolateral Membrane ◽  
Membrane Properties ◽  
Ion Permeability ◽  
Intrinsic Properties ◽  
Bathing Medium ◽  
Surface Areas ◽  
Low Protein ◽  
Convoluted Tubules ◽  
Proximal Convoluted Tubules

We examined the properties of basolateral cell membranes in "immature" and "mature" proximal tubules and evaluated the possibility that changes in those membranes might contribute to the reported maturation of tubule function. Proximal convoluted tubules were dissected in connection with superficial glomeruli, crimped at both ends, and induced to swell by use of ouabain, low protein bathing medium, and/or collagenase. Tubules from adult animals swelled faster than tubules from 2- to 5- or 14- to 17-day-old animals. However, the basolateral cell membranes of tubules from adult animals were three- to fourfold larger in surface area than those from 2- to 17-day animals, so that the ratio of the swelling rates to the measured basolateral membrane areas remained constant during the period from newborn to adult. We conclude that the basolateral membranes "mature" only in their surface areas and that little change occurs in their intrinsic properties such as hydraulic conductivity or ion permeability.

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