Selectivity of basolateral anion exchange in the acidification pathway of turtle bladder

1987 ◽  
Vol 252 (6) ◽  
pp. F1022-F1027
Author(s):  
R. F. Husted ◽  
J. L. Fischer
Keyword(s):  
Anion Exchange ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Luminal Surface ◽  
Methyl Sulfate ◽  
Conductive Pathway ◽  
Steric Factors ◽  
Solution Bathing ◽  
Anion Interaction

The turtle urinary bladder in vitro acidifies the solution bathing its luminal surface. Protons are actively extruded across the apical membrane by an H+-ATPase. Bicarbonate ion exits the cell across the basolateral membrane via a stilbene-sensitive, anion exchange for chloride. Chloride then exits the cell via a conductive pathway. The present studies were undertaken to define the specificity of the basolateral anion exchange mechanism for chloride. Turtle bladders were mounted on chambers in vitro, short-circuited, and treated with ouabain. The current remaining after inhibition of sodium transport was used to measure the acidification rate. Ion replacement studies with bromide, isethionate, sulfate, and nitrate indicated that only bromide supported acidification at rates comparable to chloride. In separate experiments, kinetic analysis of anion interaction with the exchanger indicates that maximal acidification rates decrease in the order: Cl greater than Br greater than SO4 greater than methyl sulfate = gluconate. The affinity of the exchanger decreases in the order: Cl greater than SO4 greater than Br greater than HCO3 greater than methylsulfate greater than gluconate. These selectivity sequences indicate "strong" interaction of the anions with the selectivity site. The differences in position of the polyatomic anions in the two sequences indicates that the "binding" site is accessible but that transport is limited by steric factors.

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.

Anomalous potential difference responses to changes in sodium concentration in the antrum of frog stomach

1983 ◽  
Vol 245 (4) ◽  
pp. G554-G561 ◽  
Author(s):  
G. Carrasquer ◽  
D. Kissel ◽  
W. S. Rehm ◽  
M. Schwartz
Keyword(s):  
Rana Catesbeiana ◽  
Apical Membrane ◽  
Sodium Concentration ◽  
Potential Difference ◽  
Conductive Pathway ◽  
Luminal Side ◽  
Frog Stomach ◽  
Conductance Ratio ◽  
Cl Conductance

Previously, an electrogenic Na-Cl symport was found in the fundus, and the question arises of whether there is one in the antrum, a tissue that does not secrete acid. In an in vitro preparation of the antrum of Rana catesbeiana, we found that when the [Na+] in nutrient solution was decreased (choline for Na+) the transmucosal potential difference (PD) decreased (the positivity of nutrient side decreased), and when the [Na+] was increased the PD increased. These PD changes were anomalous for Na+ but not for choline. A linear relationship for PD versus log [Na+] and not versus log [choline] excluded a choline conductive pathway. The anomalous PD response was decreased but not abolished by 10(-3) M ouabain. Normal PD responses resulted from [Na+] changes in Cl--free (SO2-4) solutions. PD responses to changes in nutrient [Cl-] were normal but decreased in the absence of Na+. Data are compatible with a passive electrogenic Na-Cl symport with more chloride than sodium ions transported per cycle, as in the fundus. Symport conductance-to-total Cl- conductance ratio is higher in antrum than in the fundus. Data from the luminal side were compatible with apical membrane conductances for Na+ and Cl-.

Electrophysiological characterization of upper portion of descending limb of long-looped nephron

1991 ◽  
Vol 260 (3) ◽  
pp. F311-F316 ◽  
Author(s):  
K. Yoshitomi ◽  
M. Imai
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
High Water ◽  
Membrane Resistance ◽  
Membrane Voltage ◽  
Major Pathway ◽  
K Concentration ◽  
Electrophysiological Characterization

The upper portion of the descending limb of long-looped nephron (LDLu) of the hamster is characterized by high water and ion permeabilities. Although the paracellular route is considered to be the major pathway representing cation permselectivity of this segment, ion transport mechanisms through the transcellular pathway are unknown. To study this issue; we applied cable analysis and conventional microelectrode technique to the hamster LDLu perfused in vitro. The transmural voltage (VT) was not different from zero, and transmural resistance (RT) was very low, 18.3 +/- 2.0 omega.cm2 (n = 12). The basolateral membrane voltage was -80 +/- 2 mV (n = 55), and fractional apical membrane resistance was 0.92 +/- 0.23 (n = 5). Ouabain (0.1 mM) in the bath decreased basolateral membrane voltage (VB) by 23 +/- 3 mV (n = 6, P less than 0.001). Increase in K+ concentration in bath and in lumen from 5 to 50 mM decreased VB by 39 +/- 2 (n = 7, P less than 0.01) and apical membrane voltage (VA) by 10 +/- 1 mV (n = 7, P less than 0.001), respectively. Addition of 2 mM Ba2+ to bath and to lumen decreased VB by -47 +/- 2 (n = 11, P less than 0.001) and decreased VA by 8 +/- 1 mV, respectively. Reduction of HCO3- in bath from 25 to 2.5 mM decreased VB by 4 +/- 1 mV (n = 7, P less than 0.005). Reduction of bath Cl- did not cause any rapid deflection of VB. No appreciable Na+ conductance was detected in the apical membrane.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium and chloride transport across the isolated porcine gallbladder

1989 ◽  
Vol 257 (1) ◽  
pp. C45-C51 ◽  
Author(s):  
S. M. O'Grady ◽  
P. J. Wolters
Keyword(s):  
Apical Membrane ◽  
Chloride Transport ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Ringer Solution ◽  
Disulfonic Acid ◽  
Ussing Chambers ◽  
Cl Secretion ◽  
Conductive Pathway

Porcine gallbladder, stripped of serosal muscle, mounted in Ussing chambers, and bathed in plasma-like Ringer solution generates a serosal positive transepithelial potential of 4-7 mV and a short-circuit current (Isc) of 50-120 microA/cm2. Substitution of Cl with gluconate or HCO3 with N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) results in a 50% decrease in Isc. Treatment with 1 mM amiloride (mucosal side) or 0.1 mM acetazolamide (both sides) causes 25-27% inhibition of the Isc. Mucosal addition of 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid inhibits the Isc by 17%. Serosal addition of 0.1 mM bumetanide inhibits the Isc by 28%. Amiloride (1 mM) inhibits the net transepithelial fluxes of Na and Cl by 55 and 41%, respectively. Substitution of Cl with gluconate inhibits the net Na flux by 50%, whereas substitution of HCO3 with HEPES inhibits 85-90% of the net Na flux and changes Cl absorption to net secretion. Based on these results, it is hypothesized that Na and Cl transport across the apical membrane is mediated by two pathways, Na-H/Cl-HCO3 exchange and Na-HCO3 cotransport. Partial recycling of Cl and HCO3 presumably occurs through a Cl conductive pathway and Cl-HCO3 exchange, respectively, in the apical membrane. This results in net Na absorption, which accounts for most of the Isc observed under basal conditions. The effect of bumetanide on the basolateral membrane and the fact that Cl secretion occurs when HCO3 is absent suggests that Cl secretion involves a basolateral NaCl or Na-K-Cl cotransport system arranged in series with a Cl conductive pathway in the apical membrane.

β-Cyclodextrin and permeability to water in the bladder of Bufo arenarum

2011 ◽  
Vol 89 (5) ◽  
pp. 311-315 ◽  
Author(s):  
G. Orce ◽  
G. Castillo ◽  
Y. Chanampa
Keyword(s):  
Apical Membrane ◽  
Basolateral Membrane ◽  
Membrane Receptors ◽  
Cholesterol Depletion ◽  
Intracellular Camp ◽  
Osmotic Gradient ◽  
Apical Side ◽  
Solution Bathing ◽  
Membrane Components ◽  
Hydrolysis Of

We measured the effect of β-cyclodextrin (BCD, a cholesterol scavenger) on water flow across the isolated toad bladder exposed to an osmotic gradient (Jw) by a gravimetric technique. BCD, when present in the solution bathing the apical side of the bladder, inhibited the increase in Jw caused by nystatin, a polyene antibiotic that acts by directly binding apical membrane cholesterol. When present in the basolateral bath, BCD inhibited the increase in Jw caused by basolateral exposure to oxytocin (which binds membrane receptors and stimulates the synthesis of cAMP), but did not alter the response to theophylline (which inhibits hydrolysis of cAMP by cyclic nucleotide phosphodiesterase). The present data are consistent with the notion that agents that increase Jw by interacting with membrane receptors, which appear to be clustered in cholesterol-rich domains of the basolateral membrane, are altered by cholesterol depletion, whereas agents that do not interact with receptors or other basolateral membrane components are not affected by this treatment. In either case, cholesterol depletion of the apical membrane does not affect the increase in Jw brought about by an increase in intracellular cAMP concentration.

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 Neonatal rabbit proximal tubule basolateral membrane Na+/H+antiporter and Cl−/base exchange

1999 ◽  
Vol 276 (6) ◽  
pp. R1792-R1797 ◽  
Author(s):  
Mehul Shah ◽  
Raymond Quigley ◽  
Michel Baum
Keyword(s):  
Proximal Tubule ◽  
Intracellular Ph ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Fluorescent Dye ◽  
Adult Rabbit ◽  
Base Exchange ◽  
Straight Tubules ◽  
Exchange Activity

The present in vitro microperfusion study examined the maturation of Na+/H+antiporter and Cl−/base exchanger on the basolateral membrane of rabbit superficial proximal straight tubules (PST). Intracellular pH (pHi) was measured with the pH-sensitive fluorescent dye 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein in neonatal and adult superficial PST. Na+/H+antiporter activity was examined after basolateral Na+ addition in tubules initially perfused and bathed without Na+. Neonatal Na+/H+antiporter activity was ∼40% that of adult segment (9.7 ± 1.5 vs. 23.7 ± 3.2 pmol ⋅ mm−1 ⋅ min−1; P < 0.001). The effect of bath Cl− removal on pHi was used to assess the rates of basolateral Cl−/base exchange. In both neonatal and adult PST, the Cl−/base exchange activity was significantly higher in the presence of 25 mM[Formula: see text] than in the absence of[Formula: see text] and was inhibited by cyanide and acetazolamide, consistent with Cl−/[Formula: see text]exchange. The proton flux rates in the presence of bicarbonate in neonatal and adult tubules were 14.1 ± 3.6 and 19.5 ± 3.5 pmol ⋅ mm−1min−1, respectively ( P = NS), consistent with a mature rate of Cl−/[Formula: see text]exchanger activity in neonatal tubules. Basolateral Cl−/base exchange activity in the absence of CO2 and[Formula: see text], with luminal and bath cyanide and acetazolamide, was greater in adult than in neonatal PST and inhibited by bath DIDS consistent with a maturational increase in Cl−/OH−exchange. We have previously shown that the rates of the apical membrane Na+/H+antiporter and Cl−/base exchanger were approximately fivefold lower in neonatal compared with adult rabbit superficial PST. These data demonstrate that neonatal PST basolateral membrane Na+/H+antiporter and Cl−/base exchanger activities are relatively more mature than the Na+/H+antiporter and Cl−/base exchangers on the apical membrane.

Membrane effects of chloride substitutes in guinea pig gallbladder epithelial cells

1989 ◽  
Vol 257 (4) ◽  
pp. C766-C774 ◽  
Author(s):  
F. Wehner ◽  
G. Sigrist ◽  
K. U. Petersen
Keyword(s):  
Epithelial Cells ◽  
Guinea Pig ◽  
Apical Membrane ◽  
Rank Order ◽  
Basolateral Membrane ◽  
Serosal Side ◽  
Membrane Effects ◽  
Microelectrode Techniques ◽  
Cl Permeability

Differences in the responses of guinea pig gallbladder epithelial cells to replacement of luminal Cl- with either isethionate (I), gluconate (G), sulfate (S), or cyclamate (C) were investigated in vitro using intracellular microelectrode techniques. In prostaglandin E1 (PGE1)-treated tissues (10(-6) M, serosal side), where electrodiffusive apical membrane Cl- permeability (PCla) is high, replacement of luminal Cl- caused transient membrane depolarizations of similar magnitudes but different times to peak (C greater than G = S greater than I). The subsequent shifts in membrane voltages were, at steady state, straight correlated with the concomitant increases in apparent ratio of apical to basolateral membrane resistances (Ra/Rb). Increases followed the rank order I greater than G = S greater than C, which was also found to be the case in the peak membrane hyperpolarizations on restoring luminal Cl-. Under control conditions (no PGE1, low PCla), three of the substitutes caused a slow hyperpolarization, C greater than G = S, whereas an I-for-Cl- substitution evoked a transient depolarization and a drop in Ra/Rb. Under both control and PGE1 conditions, a transient depolarization followed luminal I-for-C substitution. Our results are best explained by a stimulatory effect of I (and, less marked, G and S) on PCla. Intrinsic effects of cyclamate are not ruled out; however, among the substitutes examined, it is the most inert.

Diluting segment in kidney of dogfish shark. II. Electrophysiology of apical membranes and cellular resistances

1990 ◽  
Vol 258 (2) ◽  
pp. R409-R417 ◽  
Author(s):  
S. C. Hebert ◽  
P. A. Friedman
Keyword(s):  
Apical Membrane ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Short Circuit Current ◽  
Membrane Resistance ◽  
Membrane Voltage ◽  
Primary Resistance ◽  
Diluting Segment ◽  
Dogfish Shark

Diluting segments from the bundle zone of the dogfish shark kidney were perfused in vitro and the electrophysiological characteristics of this segment investigated using conventional microelectrodes and cable analysis. In 21 tubules perfused with symmetrical Ringer solutions the average transepithelial voltage (Vte), transepithelial conductance (Gte), and equivalent short circuit current (Isc) were 8.7 +/- 0.6 mV, 91.3 +/- 10.2 mS/cm2, and 641 +/- 48 microA/cm2, respectively. Microelectrode impalements in 52 cells yielded values for the basolateral membrane voltage (Vb) and an estimated apical membrane fractional resistance (fRa) of -57.5 +/- 1.3 mV and 0.896 +/- 0.008, respectively. All of these parameters were distributed in a Gaussian manner. Liminal furosemide (10(-4) M) abolished Isc, hyperpolarized apical membrane voltage (Va) and Vb, increased Gte, and reduced fRa. The apical membrane was predominantly conductive to K+: increasing luminal K+ from 5 to 49.7 mM resulted in an apical depolarization of 41.2 mV and a fall in fRa and luminal Ba2+ (1 mM) depolarized Va by 14.3 mV and increased fRa. The apical transference number for K+ was 0.74 +/- 0.07. The cellular and paracellular resistances were estimated from the effects of luminal Ba2+ on fRa and Gte. The cell conductance represented approximately 45% of Gte, with the primary resistance barrier located at the apical membrane: apical membrane resistance was 59.7 +/- 16.0 and basolateral membrane resistance was 5.9 +/- 2.3 omega.cm2. From these resistance values together with the passive permeability (PNa/PCl) of 2.5 determined previously, the ratio of net Cl- absorption to net transcellular Na+ absorption was determined to be 2.(ABSTRACT TRUNCATED AT 250 WORDS)

Furosemide blocks basolateral membrane Cl- permeability in gallbladder epithelium

1990 ◽  
Vol 258 (6) ◽  
pp. C1150-C1158 ◽  
Author(s):  
J. S. Stoddard ◽  
G. A. Altenberg ◽  
M. L. Ferguson ◽  
L. Reuss
Keyword(s):  
Anion Exchange ◽  
Apical Membrane ◽  
Basolateral Membrane ◽  
Ringer Solution ◽  
Combined Effect ◽  
Gallbladder Epithelium ◽  
K Permeability ◽  
Cl Conductance ◽  
Stimulation Of ◽  
Cl Permeability

In Necturus gallbladders bathed in a NaCl Ringer solution buffered with 10 mM HCO3(-)-1% CO2, furosemide (added to the serosal solution) caused a concentration-dependent hyperpolarization of both cell membranes that was slow and reversible. At 10(-3) M furosemide, the basolateral membrane voltage (Vcs) increased significantly from -71 +/- 3 to -85 +/- 3 mV, the depolarization of Vcs elicited by a 10-fold rise in serosal [K+] increased from 34 +/- 4 to 50 +/- 1 mV, the depolarization elicited by lowering serosal [Cl-] from 98 to 8.1 mM was reduced from 15 +/- 1 to 1 +/- 1 mV, and the depolarization in response to lowering serosal [HCO3-] from 10 to 1 mM was reduced from 13 +/- 1 to 5 +/- 0.4 mV. Furosemide could in principle decrease the basolateral membrane Cl- conductance (Gcl), increase the basolateral membrane K+ conductance, or have a combined effect. To distinguish among these possibilities, we estimated the resistance of the basolateral membrane (Rb) by means of two-point intraepithelial cable analysis experiments. Furosemide increased Rb by 22%, which indicates that furosemide reduces basolateral membrane Gcl. The effect cannot be attributed to inhibition of apical membrane anion exchange by serosal addition of furosemide, because base secretion from cells to lumen is unchanged. We conclude that furosemide blocks reversibly basolateral membrane electrodiffusive Cl- permeability. A concomitant stimulation of basolateral membrane electrodiffusive K+ permeability is also possible.

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