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  • 11
    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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  • 12
    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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  • 13
    Electronic Resource
    Electronic Resource
    Macula densa cells sense luminal NaCl concentration via furosemide sensitive Na+2Cl−K+ cotransport (1989)
    Springer
    Pflügers Archiv 414 (1989), S. 286-290 
    Details
    ISSN: 1432-2013
    Keywords: Isolated perfused tubule ; Macula densa ; Intracellular voltage ; Furosemide ; Tubuloglomerular feedback
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The macula densa cells of the juxtaglomerular apparatus probably serve as the sensor cells for the signal which leads to the appropriate tubuloglomerular feedback response. The present study reports basolateral membrane voltage (PDbl) measurements in macula densa cells. We isolated and perfused in vitro thick ascending limb segments with the glomerulus, and therefore the macula densa cells, and the early distal tubule still attached. Macula densa cells were impaled with microelectrodes under visual control. PDbl was recorded in order to examine how these cells sense changes in luminal NaCl concentrations. The addition of furosemide, a specific inhibitor of the Na+2Cl−K+ cotransporter in the thick ascending limb, to the lumen of the perfused thick ascending limb hyperpolarized PDbl from −55±5 mV to −79±4 mV (n=7). Reduction of NaCl in the lumen perfusate from 150 mmol/l to 30 mmol/l also hyperpolarized PDbl from −48±3 mV to −66±5 mV (n=4). A Cl− concentration step in the bath from 150 mmol/l to 30 mmol/l resulted in a 24±4 mV (n=4) depolarization of PDbl. This depolarization of PDbl was absent when furosemide was present during the Cl− concentration step. These data suggest that the macula densa cells sense changes in luminal NaCl concentration via coupled uptake of Na+ and Cl−. The transport pathways for NaCl transport in macula densa cells are probably identical to those in the thick ascending limb: the (Na++K+)-ATPase in the basolateral membrane drives Na+ and Cl− uptake via the luminal Na+2Cl−K+ cotransport, Cl− leaves the cell via basolateral Cl− channels and K+ recycles across the apical membrane via K+ channels. Changes in intracellular Cl− activity as a result of altered luminal NaCl uptake, and thus voltage changes of the basolateral membrane are probably the first signal in the tubuloglomerular feedback regulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584628
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  • 14
    Electronic Resource
    Electronic Resource
    Effects of glucagon on Na+, Cl−, K+, Mg2+ and Ca2+ transports in cortical and medullary thick ascending limbs of mouse kidney (1989)
    Springer
    Pflügers Archiv 414 (1989), S. 640-646 
    Details
    ISSN: 1432-2013
    Keywords: Glucagon ; Transepithelial ion net fluxes ; Na+, Cl−, K+, Ca2+, Mg2+ transport ; Electron microprobe ; Mouse kidney ; In vitro microperfusion ; Cortical and medullary thick ascending limb of Henle's loop ; In vivo micropuncture study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of glucagon on transepithelial Na+, Cl−, K+, Ca2+ and Mg2+ net fluxes were investigated in isolated perfused cortical (cTAL) and medullary (mTAL) thick ascending limbs of Henle's loop of the mouse nephron. Transepithelial ion 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. Simultaneously the transepithelial voltage (PDte) and the transepithelial resistance (R te) were recorded. In cTAL-segments (n=8), glucagon (1.2×10−8 mol · l−1) stimulated significantly the reabsorption of Na+, Cl−, Ca2+ and Mg2+∶J Na + increased from 204±20 to 228±23 pmol · min−1 · mm−1,J Cl − from 203±18 to 234±21 pmol · min−1 · mm−1,J Ca 2+ from 0.52±0.13 to 1.34±0.30 pmol · min−1 · mm−1 andJ Mg 2+ from 0.51±0.08 to 0.84±0.08 pmol · min−1 · mm−1.J K+ remained unchanged: 3.2±1.3 versus 4.0±1.9 pmol · min−1 · mm−1. Neither PDte (16.3±1.5 versus 15.9±1.4 mV) norR te (22.5±3.0 versus 20.3±2.6 Ωcm2) were changed significantly by glucagon. However, in the post-experimental periods a significant decrease in PDte and increase inR te were noted. In mTAL-segments (n=9), Mg2+ and Ca2+ transports were close to zero and glucagon elicited no significant effect. The reabsorptions of Na+ and Cl−, however, were strongly stimulated:J Na + increased from 153±17 to 226±30 pmol · min−1 · mm−1 andJ Cl − from 151±23 to 243±30 pmol · min−1 · mm−1. The rise in NaCl transport was accompanied by an increase in PDte from 10.3±1.1 to 12.3±1.2 mV and a decrease inR te from 19.1±2.7 to 17.8±2.0 Ωcm2. No net K+ movement was detectable either in the absence or in the presence of glucagon. A micropuncture study carried out in hormone-deprived rats indicated that glucagon stimulates Na+, Cl−, K+, Mg2+ and Ca2+ reabsorptions in the loop of Henle. In conclusion our data demonstrate that glucagon stimulates NaCl reabsorption in the mTAL segment and to a lesser extent in the cTAL segment whereas it stimulates Ca2+ and Mg2+ reabsorptions only in the cortical part of the thick ascending limb of the mouse nephron. These data are in good agreement with, and extend, those obtained in vivo on the rat with the hormone-deprived model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582129
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  • 15
    Electronic Resource
    Electronic Resource
    Aufnahme von 2-C14 Harnsäure in die Erythrocyten von Patienten mit Hyperurikämie und Gicht (1975)
    Springer
    Journal of molecular medicine 53 (1975), S. 261-264 
    Details
    ISSN: 1432-1440
    Keywords: Urat uptake ; erythrocyte ; hyperuricemia ; gout ; Harnsäureaufnahme ; Erythrocyt ; Hyperurikämie ; Gicht
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei 19 Patienten mit primärer Hyperurikämie, 6 mit sekundärer Hyperurikämie, 17 mit primärer Gicht und 30 Kontrollpersonen wird die Aufnahme von 2-C14 Harnsäure in die Erythrocyten gemessen. Es zeigt sich, daß die Erythrocyten von Gichtpatienten signifikant weniger Harnsäure aufnehmen als die von Kontroilpersonen. Dagegen unterscheiden sich die primären und sekundären Hyperurikämiepatienten nicht signifikant von den Kontrollen. Der Unterschied in der Aufnahme von Harnsäure bei Erythrocyten von Gichtpatienten und Kontrollen betrifft hauptsächlich den Anfangsteil der Aufnahmekinetik. Es wird die mögliche pathophysiologische Bedeutung der verminderten Harnsäureaufnahme für das Entstehen der Harnsäurepräcipitationen bei Gicht diskutiert und auf die Möglichkeit hingewiesen, den Harnsäure-Tracer-Aufnahmetest als diagnostisches Hilfsmittel für die Früherkennung der Gicht anzuwenden.
    Notes: Summary The uptake of 2-C14 urate by erythrocytes was measured in 19 patients with primary hyperuricemia, 6 patients with secondary hyperuricemia, 17 patients with primary gout and 30 controls. The uptake of urate in patients with primary gout was significantly lower than in the controls. In contrast no such difference could be observed in patients with primary and secondary hyperuricemia. The uptake of labeled urate by erythrocytes from gouty patients is especially diminished in the early phase of the uptake kinetics. The possible relevance of this finding for the pathogenesis of urate precipitation in gout is discussed. Further, we consider the application of the tracer urate uptake by erythrocytes as an aid in the early diagnosis of gout.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01469117
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  • 16
    Electronic Resource
    Electronic Resource
    Effect of benzolamide on luminal pH in proximal convoluted tubules of the rat kidney (1978)
    Springer
    Pflügers Archiv 375 (1978), S. 39-43 
    Details
    ISSN: 1432-2013
    Keywords: Proximal tubule ; Micropuncture ; Carbonic anhydrase ; Benzolamide ; Acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Luminal pH in early and late proximal tubules was recorded continuously with antimony microelectrodes before and during carbonic anhydrase inhibition. Following i.v. application of benzolamide (25 μmol/kg BW), luminal pH decreased almost immediately in early proximal tubules (ΔpH −0.42±0.06 SEM), but increased in late proximal tubules (ΔpH +0.27±0.06). Urinary pH increased (ΔpH +1.6±0.16) after a delay of some 30 s. Similar results, i.e. decrease of pH in early and increase of pH in late proximal tubules, were obtained, when benzolamide containing solutions were microinfused into early proximal tubules or superfused on the nephron surface. In contrast, luminal pH decreased in late proximal tubules, when benzolamide was microinfused into the same nephron segment. The decrease of luminal pH indicates inhibition of luminally active carbonic anhydrase, leading to delayed buffering of secreted hydrogen ions. The increase of luminal pH in late proximal tubules may be attributed to several factors including increased delivery of bicarbonate, impaired bicarbonate exit at the antiluminal membrane and decreased hydrogen ion formation in the tubular cell due to inhibition of cellular carbonic anhydrase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584146
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  • 17
    Electronic Resource
    Electronic Resource
    Handling of oxalate by the rat kidney (1978)
    Springer
    Pflügers Archiv 374 (1978), S. 243-248 
    Details
    ISSN: 1432-2013
    Keywords: Oxalate ; Wistar rat ; Microperfusion ; Microinfusion ; Organic acid secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Renal transport of14C-oxalate was studied in the rat by clearance and micropuncture techniques. The ultrafilterability of oxalate was 0.98±0.02 (n=7). Fractional clearance of oxalate was significantly above unity in antidiuresis and volume expansion: mean 1.24 ±0.04 (n=115). Pyrazinamide (1.1·10−3 mol/kg BW) and probenecid (0.35·10−3 mol/kg BW) had no significant effect on oxalate clearance. P-aminohippurate (1.45·10−3 mol/kg BW) and urate (0.48 ·10−3 mol/kg BW) depressed the fractional clearance of oxalate significantly from 116 to 91 and from 125 to 90%, respectively. Excess excretion of14C-oxalate over3H-inulin was invariably demonstrable in peritubular microperfusion experiments (n=5) and in microinfusions underneath the kidney capsule (n=4). Together with the first 50% of3H-inulin 58±2% of the total14C-oxalate were excreted in the peritubular microperfusions, and 64±3% in the subcapsular microinfusions. In tubular microinfusion experiments (n=36) urinary14C-oxalate recovery was almost complete after early proximal microinfusion (93±4%) and complete after late proximal microinfusion (102±4%). In continuous microperfusion experiments of proximal tubules (n=42) a small but highly significant outflux of14C-oxalate of 7% per mm perfusion distance was found. The data suggest that oxalate is freely filterable at the glomerular site. A small but significant amount of oxalate is reabsorbed in the proximal nephron. Most likely at the same site and in the pars recta oxalate is secreted and tubular load increased to 124% of filtered load. This amount is excreted in final urine. The secretion of oxalate is inhibited by organic acids which are known to be secreted by the proximal tubule and the pars recta.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585601
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  • 18
    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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  • 19
    Electronic Resource
    Electronic Resource
    Preface (1986)
    Springer
    Pflügers Archiv 407 (1986), S. S59 
    Details
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584930
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  • 20
    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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