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  • 1
    Electronic Resource
    Electronic Resource
    Chloride Transport in Thick Ascending Limb, Distal Convolution, and Collecting Duct (1988)
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 50 (1988), S. 111-122 
    Details
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1146/annurev.ph.50.030188.000551
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of ouabain and temperature on cell membrane potentials in isolated perfused straight proximal tubules of the mouse kidney (1986)
    Springer
    Pflügers Archiv 407 (1986), S. 252-257 
    Details
    ISSN: 1432-2013
    Keywords: Proximal tubule ; Kidney ; K+ conductance ; Cell membrane potential ; Ouabain temperature ; Phlorizin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In isolated perfused segments of the mouse proximal tubule, the potential difference across the basolateral cell membrane (PDbl) was determined with conventional microelectrodes. Under control conditions with symmetrical solutions it amounted to −62±1 mV (n=118). The potential difference across the epithelium (PDte) was −1.7±0.1 mV (n=45). Transepithelial resistance amounted to 1.82±0.09 kΩ cm (n=28), corresponding to 11.4±0.6 Ω cm2. Increasing bath potassium concentration from 5 to 20 mmol/l depolarized PDbl by +24±1 mV (n=103), and PDte by +1.6±0.1 mV (n=19). Thus, the basolateral cell membrane is preferably conductive to potassium. Rapid cooling of the bath perfusate from 38°C to 10°C led to a transient hyperpolarization of PDbl from −60±1 to −65±1 mV (n=21) within 40 s followed by gradual depolarization by +18±1% (n=14) within 5 min. The transepithelial resistance increased significantly from 1.78±0.11 kΩ cm to 2.20±0.21 kΩ cm (n=15). Rapid rewarming of the bath to 38°C caused a depolarization from −61±2 mV (n=17) to −43±2 mV (n=16) within 15 s followed by a repolarization to −59±2 mV (n=10) within 40 s. Ouabain invariably depolarized PDbl. During both, sustained cooling or application of ouabain, the sensitivity of PDbl to bath potassium concentration decreased in parallel to PDbl pointing to a gradual decrease of potassium conductance. Phlorizin hyperpolarized the cell membrane from −59±2 to −66±1 mV (n=13), virtually abolished the transient hyperpolarization under cooling, and significantly reduced the depolarization after rewarming from +17±2 mV (n=16) to +9±3 mV (n=9). The present data indicate that the contribution of peritubular potassium conductance to the cell membrane conductance decreases following inhibition of basolateral (Na++K+)-ATPase. Apparently, cooling from 37° to 10°C does not only reduce (Na−+K+)-ATPase activity but in addition luminal sodium uptake mechanisms such as the sodium glucose cotransporter. As a result, cooling leads to an initial hyperpolarization of the cell followed by depolarization only after some delay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585299
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  • 3
    Electronic Resource
    Electronic Resource
    Characterization of human sweat duct chloride conductance by chloride channel blockers (1987)
    Springer
    Pflügers Archiv 408 (1987), S. 511-514 
    Details
    ISSN: 1432-2013
    Keywords: Human sweat duct ; Cl− conductance ; Cl− channel blockers ; Cystic fibrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To characterize the chloride conductance of human sweat duct the effect of various analogues of diphenylamine-2-carboxylate was investigated on the transepithelial potential difference (PDT) and resistance (R T ) of isolated microperfused sweat ducts. Although the most powerful analogues which block Cl− channels in various secretory and absorptive epithelia were ineffective, a number of analogues (in particular Cl substituted ones) were found which at high concentrations significantly and reversibly increased PDT andR T . The data suggest that the main chloride conductance pathway of sweat duct epithelium resides in the cell membranes rather than in the tight junctions. In addition the different blocking spectra of the chloride conductances of sweat duct and tracheal epithelium (Welsh MJ, Science 232:1648, 1986) suggest that the combined impairment of both conductances in cystic fibrosis does not result from a molecular defect in the Cl− channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585077
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  • 4
    Electronic Resource
    Electronic Resource
    The diuretic effect of muzolimine (1987)
    Springer
    Pflügers Archiv 410 (1987), S. 674-676 
    Details
    ISSN: 1432-2013
    Keywords: Muzolimine ; Na+2Cl−K+ cotransporter ; thick ascending limb of the loop of Henle ; loop diuretics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Muzolimine produces a diuresis in the loop of Henle. Unlike other diuretics of this kind, the effect of muzolimine is slow and its action is long lasting. The present study was designed to examine the mechanism of action of muzolimine in isolated in vitro perfused rabbit cortical thick ascending limb segments (cTAL). In a first series it was confirmed that muzolimine itself in a concentration of up to 10−4 mol/l had no effect on the equivalent short circuit current (Isc), corresponding to the rate of active NaCl reabsorption, in cTAL segments neither from the lumen nor from the bath side. In a second series of experiments, muzolimine was administered intravenously (70 μmol/kg) to male Wistar rats, and the clearances of inulin, Na+ and K+ were calculated. Muzolimine, after a lag phase of 5 to 20 min caused a marked diuresis and natriuresis, but had only a minor effect on glomerular filtration rate and on K+ excretion. The urines of these animals were diluted with isotonic saline, and were examined in rabbit cTAL segments for their ability to block Isc. It was found that the urines of the antidiuretic period were devoid of effects, whereas the diuretic urines inhibited Isc strongly down to a dilution of 300 times when they were perfused in the lumen. The same diluted urines had no effect from the bath side. In a third series, probenecid (100 μmol/kg) was administered i.v. to rats undergoing a muzolimine induced saluresis. It was found that probenecid inhibited the diuresis and saluresis. The present data indicate (i) that muzolimine itself has no diuretic potency, (ii) that the substance is metabolized in the intact animal and that a diuretic metabolite is generated, (iii) that this active metabolite is accumulated in tubule fluid by proximal secretion, and (iv) that it inhibits active NaCl transport in the cTAL segment from the lumen side.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581331
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  • 5
    Electronic Resource
    Electronic Resource
    Electrophysiological study of transport systems in isolated perfused pancreatic ducts: properties of the basolateral membrane (1988)
    Springer
    Pflügers Archiv 411 (1988), S. 58-68 
    Details
    ISSN: 1432-2013
    Keywords: Pancreas ; Isolated perfused ducts ; HCO 3 − transport ; K+ conductance ; (Na++K+)-ATPase ; Na+/H+ antiport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the mechanism of pancreatic HCO 3 − transport, a perfused preparation of isolated intra-and interlobular ducts (i.d. 20–40 μm) of rat pancreas was developed. Responses of the epithelium to changes in the bath ionic concentration and to addition of transport inhibitors was monitored by electrophysiological techniques. In this report some properties of the basolateral membrane of pancreatic duct cells are described. The transepithelial potential difference (PDte) in ducts bathed in HCO 3 − -free and HCO 3 − -containing solution was −0.8 and −2.6 mV, respectively. The equivalent short circuit current (Isc) under similar conditions was 26 and 50 μA·cm−2. The specific transepithelial resistance (Rte) was 88 Ωcm2. In control solutions the PD across the basolateral membrane (PDbl) was −63±1 mV (n=314). Ouabain (3 mmol/l) depolarized PDbl by 4.8±1.1 mV (n=6) within less than 10 s. When the bath K+ concentration was increased from 5 to 20 mmol/l, PDbl depolarized by 15.9±0.9 mV (n=50). The same K+ concentration step had no effect on PDbl if the ducts were exposed to Ba2+, a K+ channel blocker. Application of Ba2+ (1 mmol/l) alone depolarized PDbl by 26.4±1.4 mV (n=19), while another K+ channel blocker TEA+ (50 mmol/l) depolarized PDbl only by 7.7±2.0 mV (n=9). Addition of amiloride (1 mmol/l) to the bath caused 3–4 mV depolarization of PDbl. Furosemide (0.1 mmol/l) and SITS (0.1 mmol/l) had no effect on PDbl. An increase in the bath HCO 3 − concentration from 0 to 25 mmol/l produced fast and sustained depolarization of PDbl by 8.5±1.0 mV (n=149). It was investigated whether the effect of HCO 3 − was due to a Na++-dependent transport mechanism on the basolateral membrane, where the ion complex transferred into the cell would be positively charged, or whether it was due to decreased K+ conductance caused by lowered intracellular pH. Experiments showed that the HCO 3 − effect was present even when the bath Na+ concentration was reduced to a nominal value of 0 mmol/l. Similarly, the HCO 3 − effect remained unchanged after Ba2+ (5 mmol/l) was added to the bath. The results indicate that on the basolateral membrane of duct cells there is a ouabain sensitive (Na++K+)-ATPase, a Ba2+ sensitive K+ conductance and an amiloride sensitive Na+/H+ antiport. The HCO 3 − effect on PDbl is most likely due to rheogenic anion exit across the luminal membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581647
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  • 6
    Electronic Resource
    Electronic Resource
    Properties of the luminal membrane of isolated perfused rat pancreatic ducts (1988)
    Springer
    Pflügers Archiv 411 (1988), S. 546-553 
    Details
    ISSN: 1432-2013
    Keywords: Pancreas ; Isolated perfused ducts ; Luminal membrane ; Cl− conductance ; Cl−/HCO 3 − antiport ; cAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present study was to investigate by what transport mechanism does HCO 3 − cross the luminal membrane of pancreatic duct cells, and how do the cells respond to stimulation with dibytyryl cyclic AMP (db-cAMP). For this purpose a newly developed preparation of isolated and perfused intra-and interlobular ducts of rat pancreas was used. Responses of the epithelium to inhibitors and agonists were monitored by electrophysiological techniques. Addition of HCO 3 − /CO2 to the bath side of nonstimulated ducts depolarized the PD across the basolateral membrane (PDbl) by about 9mV, as also observed in a previous study [21]. This HCO 3 − effect was abolished by Cl− channel blockers or SITS infused into the lumen of the duct: i. e. 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 10−5 M) hyperpolarized PDbl by 8.2±1.6 mV (n=13); 3′,5-dichlorodiphenylamine-2-carboxylic acid (DCl-DPC, 10−5 M) hyperpolarized PDbl by 10.3±1.7 mV (n=10); and SITS hyperpolarized PDbl by 7.8±0.9 mV (n=4). Stimulation of the ducts with dbcAMP in the presence of bath HCO 3 − /CO2 resulted in depolarization of PDbl, the ductal lumen became more negative and the fractional resistance of the luminal membrane decreased. Together with forskolin (10−6 M), db-cAMP (10−4 M) caused a fast depolarization of PDbl by 33.8±2.5 mV (n=6). When db-cAMP (5×10−4 M) was given alone in the presence of bath HCO 3 − /CO2, PDbl depolarized by 25.3±4.2 mV (n=10). In the absence of exogenous HCO 3 − , db-cAMP also depolarized PDbl by 24.7±3.0 mV (n=10). The present data suggest that in the luminal membrane of pancreatic duct cells there is a Cl− conductance in parallel with a Cl−/HCO 3 − antiport. Dibutyryl cyclic AMP increases the Cl− conductance of the luminal membrane. Taking together our present results, and the recent data obtained for the basolateral membrane [21], a tentative model for pancreatic HCO 3 − transport is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582376
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  • 7
    Electronic Resource
    Electronic Resource
    Differential effects of ADH on sodium, chloride, potassium, calcium and magnesium transport in cortical and medullary thick ascending limbs of mouse nephron (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 516-523 
    Details
    ISSN: 1432-2013
    Keywords: ADH ; Transepithelial ion net fluxes ; Na+, Cl−, K+, Ca2+ and Mg2+ transport ; Electron microprobe ; Mouse kidney ; Cortical and medullary thick ascending limb of Henle's loop ; In vitro microperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of antidiuretic hormone (arginine vasopressin, AVP) on transepithelial Na+, Cl−, K+, Ca2+ and Mg2+ net transports was investigated in medullary (mTAL) and cortical (cTAL) segments of the thick ascending limb (TAL) of mouse nephron, perfused in vitro. Transepithelial net fluxes (J Na +,J Cl −,J K +,J Ca 2+,J Mg 2+) were determined by electron probe analysis of the collected tubular fluid. Transepithelial potential difference (PDte) and transepithelial resistance (Rte) were measured simultaneously. cTAL segments were bathed and perfused with isoosmolal, HCO 3 − containing Ringer solutions, mTAL segments were bathed and perfused with isoosmolal HCO 3 − free Ringer solutions. In cTAL segments, AVP (10−10 mol·l−1) significantly increasedJ Mg 2+ andJ Ca 2+ from 0.39±0.08 to 0.58±0.10 and from 0.86±0.13 to 1.19±0.15 pmol·min−1 mm−1 respectively. NeitherJ Na + norJ Cl −, (J Na +: 213±30 versus 221±28 pmol·min−1 mm−1,J Cl −: 206±30 versus 220±23 pmol·min−1 mm−1) nor PDte (13.4±1.3 mV versus 14.1±1.9 mV) or Rte (24.6±6.5Ω cm2 versus 22.6±6.4Ω cm2) were significantly changed by AVP. No significant effect of AVP on net K+ transport was observed. In mTAL segments, Mg2+ and Ca2+ net transports were close to zero and AVP (10−10 mol·l−1) elicited no effect. However NaCl net reabsorption was significantly stimulated by the hormone,J Na + increased from 107±33 to 148±30 andJ Cl − from 121±33 to 165±32 pmol·min−1 mm−1. The rise inJ NaCl was accompanied by an increase in PDte from 9.0±0.7 to 13.5±0.9 mV and a decrease in Rte from 14.4±2.0 to 11.2±1.7 Ω cm2. No K+ net transport was detected, either under control conditions or in the presence of AVP. To test for a possible effect of HCO 3 − on transepithelial ion fluxes, mTAL segments were bathed and perfused with HCO 3 − containing Ringer solutions. With the exception ofJ Ca 2+ which was significantly different from zero (J Ca 2+: 0.26±0.06 pmol·min−1 mm−1), net transepithelial fluxes of Na+, Cl−, K+ and Mg2+ were unaffected by HCO 3 − . In the presence of AVP,J Mg 2+ andJ Ca 2+ were unaltered whereasJ NaCl was stimulated to the same extent as observed in the absence of HCO 3 − . In conclusion our results indicate heterogeneity of response to AVP in cortical and medullary segments of the TAL segment, since AVP stimulates Ca2+ and Mg2+ reabsorption in the cortical part and Na+ and Cl− reabsorption in the medullary part of this nephron segment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582541
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  • 8
    Electronic Resource
    Electronic Resource
    Torasemide inhibits NaCl reabsorption in the thick ascending limb of the loop of Henle (1986)
    Springer
    Pflügers Archiv 407 (1986), S. 611-614 
    Details
    ISSN: 1432-2013
    Keywords: Torasemide ; Na+2Cl−K+ carrier ; Cl−-channel ; Thick ascending limb of the loop of Henle ; Mouse ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Torasemide (1-isopropyl-(4-(3-methylphenylamino)pyrid-3-yl)urea) is a new diuretic. The present study examines the effects of this substance in the isolated perfused thick ascending limb (TAL) of mouse and rabbit kidney. In cortical TAL segments of the rabbit, torasemide added to the lumen perfusate led to a fall in equivalent short circuit current (= transepithelial voltage divided by transepithelial resistance, which corresponds to the rate of chloride reabsorption) with a half maximal inhibition concentration of 3 · 10−7 mol/l. This effect was accompanied by a hyperpolarization of the luminal and basolateral membrane from −78 to −81 mV and from −72 to −81 mV, respectively. A similar hyperpolarization of both membrane voltages was also observed in medullary TAL segments of the mouse. Torasemide, added to the basolateral perfusate of cortical TAL segments of the rabbit, also inhibited the equivalent short circuit current. However, 3 · 10−5 mol/l were necessary for a half maximal inhibition. The fall in the equivalent short circuit current was accompanied by a significant increase in transepithelial resistance from 34 to 38 Ω cm2, by an increase in the fractional resistance of the basolateral membrane, and by a hyperpolarization mainly of the basolateral membrane. Again, similar results were obtained in the medullary TAL segment of the mouse. The strong inhibitory effect of torasemide from the lumen side can be explained by an interference with the Na+ 2Cl−K+ carrier in the luminal membrane. In fact, torasemide apparently is structurally related to furosemide. The weaker effect of torasemide from the peritubular side can, at least in part, be explained as an interference with chloride channels present in the basolateral membrane. Torasemide is also structurally related to chloride channel blockers such as diphenylamine-2-carboxylate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582640
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  • 9
    Electronic Resource
    Electronic Resource
    A voltage-dependent ionic channel in the basolateral membrane of late proximal tubules of the rabbit kidney (1986)
    Springer
    Pflügers Archiv 407 (1986), S. S142 
    Details
    ISSN: 1432-2013
    Keywords: Late proximal tubule (pars recta) ; Patch-clamp ; Basolateral membrane ; Ionic channel ; Diphenylamine-2-carboxylate ; SITS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The patch-clamp method was applied to the lateral membrane of late proximal tubules of the rabbit kidney. Tubule segments were cannulated on one side by a perfusion system. At the noncannulated end of the tubules, the lateral membrane was accessible to a patch pipette. In cell-attached, as well as cell-excised (presumably inside-out oriented) membrane patches, a voltage sensitive channel was observed. The open-state probability of this channel increased with depolarizing potentials. In cell-excised patches bathed with NaCl-Ringer on both sides, the single channel conductance g was 28.0±1.2 pS (n=10). With KCl-Ringer in the pipette and NaCl-Ringer in the bath g was 24.7±1.3 pS (n=7) and the current-voltage curve crossed the axis at 0 mV. Therefore, the channel does not discriminate between K+ and Na+ ions. Replacing half of NaCl by mannitol on the bath side yielded a permeability for cations about twice as high as for Cl−. The channel could be reversibly blocked by diphenylamine-2-carboxylate (DPC), whereas its inhibition by SITS was only partially reversible. In cell-attached patches, the channel was nearly inactivated at zero clamp potential, but became active when the membrane patch was depolarized. The significance of this nonselective channel for proximal tubule cell function is still unclear. It could be involved in the contraluminal exit mechanism of various anions. However, it could also play a role in cell volume regulation processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584943
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  • 10
    Electronic Resource
    Electronic Resource
    Piretanide-dextran and piretanide-polyethylene glycol interact with high affinity with the Na+ 2 Cl− K+ cotransporter in the thick ascending limb of the loop of Henle (1989)
    Springer
    Pflügers Archiv 413 (1989), S. 559-561 
    Details
    ISSN: 1432-2013
    Keywords: Isolated perfused tubule ; cTAL ; Na+ 2Cl− K+ cotransporter ; piretanide ; macromolecular probe
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Piretanide blocks the Na+ 2Cl− K+ cotransporter protein in the thick ascending limb (TAL) of the loop of Henle reversibly. When tested from the luminal side in isolated perfused cTAL segments it leads to a half maximal inhibition (IC50) of the equivalent short circuit current (Isc) at a concentration of 10−6 mol/l. From the basolateral side it has no effect on Isc up to 10−4 mol/l. The present study was designed to search for high affinity blockers of the Na+ 2Cl− K+ cotransporter with large molecular weight in an attempt to use these macromolecules for antibody-labelling or affinity separation of this transport-protein. Amino-ethyl-dextran or amino-ethyl-polyethylene glycol (M.W. 5kd) were coupled to isothiocyanato-piretanide (ISO-PIR) at room temperature in DMSO. The resulting compounds dextran-sulfonylurea-piretanide (PIR-DEX) and polyethylene glycol-sulfonylurea-piretanide (PIR-PEG) (M.W. 5.38kd) were purified and tested in isolated perfused cTAL segments. IC50 values for ISO-PIR, PIR-DEX and PIR-PEG were estimated from dose response curves after their addition to the lumen or bath perfusate, respectively. ISO-PIR, PIR-DEX and PIR-PEG acted from the lumen side at 3·10−6, 6·10−6 and 2·10−6 mol/l. The inhibitory effect was easily reversible. From the basolateral side no effect for any compound was seen at up to 10−4 mol/l. In clearance experiments PIR-DEX was given to female Wistar rats as an i.v. bolus (25 μmol/kg) and the diuretic urine was collected. After dialysis (exclusion limit 2.5kd) the dialysed urine and the dialysate were tested in isolated perfused cTAL segments. The dialysates had no effect on Isc, but the dialysed urine inhibited Isc by 35% from the luminal side. The present data show: High molecular derivatives of piretanide with dextran or polyethylene glycol moieties block the Na+ 2Cl− K+ cotransporter in cTAL segments at roughly the same low concentration as piretanide itself. Our data exclude a metabolism of these piretanide compounds in the kidney. Since these macromolecular probes can probably not enter the cell their inhibitory effect indicates that the binding site for piretanide diuretics on the Na+ 2Cl− K+ cotransporter is exposed on the surface of the luminal cell membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00594189
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