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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 60 (1982), S. 1165-1172 
    ISSN: 1432-1440
    Keywords: Epithelial transport ; Kidney ; Lactate transport ; Electrolyte transport ; Epithelialer Transport ; Niere ; Laktattransport ; Elektrolyttransport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Resorption bzw. Sekretion im proximalen Nierentubulus läuft einmal passiv auf dem parazellulären Weg, d.i. zwischen den Zellen hindurch, ab, zum anderen aktiv, transzellulär, durch die Zellen hindurch. Der transzelluläre aktive Transport ist in der Regel sekundär aktiv. Er verläuft gekoppelt an den Fluß von Na+-Ionen, wobei ein transzellulärer Gradient von Na+-Ionen, der seinerseits durch die kontraluminal gelegene (Na+-K+)-ATPase geschaffen wird, die Triebkraft liefert. Einmal in der Zelle, verlassen die Substanzen die kontraluminale Zellseite vermittels Karrier, die Na+-unabhängig sind. Mit Hilfe von Mikroperfusions- und elektrophysiologischen Techniken sowie mit Hilfe von Bürstensaumvesikeln wurde der Na+-Kotransport von Aminosäuren, Phosphat, Sulfat, Thiosulfat, Gallensäuren, aliphatischen und aromatischen Monokarboxylsäuren (Laktat) sowie der von Dikarboxylsäuren untersucht. Besonderes Augenmerk wurde dem bidirektionalen Transport von Thiosulfat sowie der Spezifität des Mono- und Dikarboxylsäure-Transportsystems gewidmet.
    Notes: Summary The transport through the epithelial cell layer of the renal proximal tubule proceeds in principle by passive paracellular and active transcellular transport. The active transcellular transport is mostly secondary active. This means it proceeds coupled with the flux of Na+ ions, where-by the transcellular gradient of sodium, created by the (Na++K+)-ATPase, located at the contraluminal cell side, provides the main driving force. Once in the cell the substances leave the other cell side by a Na+-independent, but carrier-mediated transport system. Using microperfusion and electrophysiological techniques as well as brush border membrane vesicle preparation the Na+-H+ countertransport and the Na+-cotransport of amino acids, phosphate, sulfate, thiosulfate, bile acids, aliphatic-aromatic monocarboxylic acids (lactate) and dicarboxylic acids was studied. Special emphasis will be given to the bidirectional transport of thiosulfate as well as to the specificity of the monocarboxylic acid and dicarboxylic acid transport system.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 57 (1979), S. 977-991 
    ISSN: 1432-1440
    Keywords: Epithelial transport ; Kidney ; Small intestine ; Electrolyte ; Epithelialer Transport ; Niere-Darm-Elektrolyt ; Elektrochemisches Gradient
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Das Epithel von Niere und Darm besteht aus einer einzigen Lage von Zellen, die an ihrer luminalen Seite durch Schlußleisten zusammengekittet sind. Der Stofftransport geht entweder transzellulär durch die Zellen hindurch und ist dann in der Regel aktiv, oder er geht parazellulär an den Zellen vorbei durch die Schlußleisten und interzellulären Spalten und ist dann passiv. Die Triebkraft für den aktiven Transport kommt entweder direkt aus dem Stoffwechsel und wirkt mittels ATPasen auf die zu transportierenden Stoffe. Wir haben dann einen primär aktiven Transport vor uns. Oder sie kommt aus Gradienten von Substanzen, in erster Linie Natriumionen, die ihrerseits primär aktiv transportiert wurden. Man spricht dann von sekundär aktivem Transport. Die Triebkräfte für den passiven Transport sind Konzentrations- bzw. elektrochemische Potentialdifferenzen sowie der durch Reibung bedingte Mitreißeffekt des resorbierten Wassers. Sowohl in Niere als auch im Darm haben die proximalen Abschnitte, wo eine große Flüssigkeitsmenge isoton resorbiert wird, undichte Schlußleisten, so daß eine beträchtliche Substanzmenge passiv resorbiert werden kann. In den distalen Abschnitten hingegen, wo der Transport geregelt wird, sind die Schlußleisten dicht, so daß entsprechende Konzentrationsunterschiede erzeugt und aufrecht erhalten werden können. Aktiver Transport durch die Epithelzellen hindurch ist indessen nur möglich, wenn der Stofftransport polar ist, d.h. an der luminalen Zellseite anders als an der kontraluminalen Zellseite. Durch elektrophysiologische Messungen an den einzelnen Zellseiten als auch durch Transportmessungen an geschlossenen Vesikeln, die von den beiden Zellseiten gewonnen wurden, konnten die treibenden Kräfte für die einzelnen Substanzen weitgehend festgelegt werden. An Schemata, in die die Transportmechanismen der einzelnen Zellseiten eingezeichnet sind, wird eine weitgehende Identität der Transportmechanismen im proximalen Tubulus und Dünndarm deutlich.
    Notes: Summary Epithelia of kidney and small intestine consist of one layer of cells which, at their luminal edge, are linked together by terminal bars. Solute transport proceeds either across the cells, which is true of all active transports, or it proceeds paracellularly through the basolateral spaces and terminal bars and is then passive. The driving force for the active transport of a substance is derived either directly from metabolism (primary active transport), or from the gradient of another solute, usually Na+, which in turn is created by primary active transport. In the latter case the transport is referred to as secondary active. The driving forces of passive transport are the electrochemical gradient of the respective substance and solvent drag. The proximal parts of the kidney as well as of the intestine are leaky so that a considerable part of net reabsorption proceeds passively. Their distal parts, however, where the transport is regulated, are tight so that large concentration differences can be created and maintained. Transcellular active transport is only possible if the cells are polar, i.e., the transport characteristics of the luminal cell membrane differ from those of the contraluminal cell membrane. By measuring the cellular electrical potential difference or by measuring transport into isolated plasma membrane vesicles from either cell side the driving forces for the two transport steps, the luminal and contraluminal, have been elucidated. Schemes for the transport steps in the proximal tubule and in the small intestine are given. They show the principal similarity of the transport of many substances in both epithelia.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The transport theory of Kedem and Katchalsky which was derived for passive transport in a two-compartment system is generalized for a multicomponent system with active transport, so that it can be applied to more complicated biological membranes. Equations have been derived to describe the transport of urea through the proximal convolution of the rat kidney and the permeability and the reflection coefficient have been determined. The permeability coefficient $$(\tilde P_u )$$ measured with the microperfusion and stop flow microperfusion methods, was found to be 6.0 and 5.2×10−5 mm2/sec, respectively. The reflection coefficient (σ) was determined in a stationary state situation and found to be 0.68. Earlier free flow micropuncture results together with theP u andσ u of this study indicate that 50% of the filtered urea is reabsorbed proximally and that approximately half of this amount is reabsorbed by solvent drag and the rest by diffusion. In the Appendix, a theoretical treatment of nonelectrolyte transport in a multicomponent system with active transport is given.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 41 (1979), S. 181-195 
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Physiology 25 (1963), S. 91-142 
    ISSN: 0066-4278
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Medicine , Biology
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 139 (1966), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Annals of the New York Academy of Sciences 341 (1980), S. 0 
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 404 (1985), S. 293-299 
    ISSN: 1432-2013
    Keywords: Epithelial transport ; Contraluminal cell membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the specificity for the contraluminal sulfate transport system the inhibitory potency of sulfate esters and sulfonate compounds on the35SO 4 2− influx from the interstitium into cortical tubular cells in situ has been determined. The following was found: 1. From 10 sulfate monoesters tested 9 inhibited contraluminal sulfate influx with an app.K i between 0.6 and 6 mmol/l; the two sulfate diesters tested, however, did not. 2. Out of 8 aliphatic sulfonate compounds only three, having a NH- or OH-group in a suitable position, exerted a moderate inhibition (app.K i ca. 2–6 mmol/l). 3. Amongst 14 benzene sulfonates tested only 2 compounds (5-nitrobenzene-sulfonate and 2-hydroxy-5-nitrobenzenesulfonate) inhibited with aK i〈5 mmol/l. 4. Out of 10 naphthalene sulfonates tested 8 inhibited with aK i〈5; the highest inhibition was seen with the NH-containing 8-anilinonaphthalene-1-sulfonate (ANS), but no inhibition with 2 compounds containing an amino group. 5. From the polycyclic sulfonates pyrene-3-sulfonate and anthracene-1-sulfonate inhibited with aK i of approximately 2 mmol/l, while no inhibition was seen with anthracene-2-sulfonate. 6. Out of 4 amino-sulfonates tested benzene-1-amino-sulfonate and a similar benzyl-analog inhibited with aK i of 1 mmol/l and smaller; cyclohexyl-1-amino-sulfonate (cyclamate), however, inhibited only slightly (app.K i of 6 mmol/l). The data indicate that sulfate monoesters are well accepted by the contraluminal sulfate transport system. The affinity of sulfonate compounds to this system depends on neighbouring OH-groups −NH-groups, meta-positioned electronegative groups or a hydrophobic moiety in an appropriate position.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 404 (1985), S. 300-306 
    ISSN: 1432-2013
    Keywords: Epithelial transport ; Contraluminal cell membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the specificity for the contraluminal sulfate transport system the inhibitory potency of disulfonates, di-, tricarboxylates and sulfocarboxylates on the35SO 4 2− influx from the interstitium into cortical tubular cells in situ has been determined. The following was found: 1) Methane- and ethane-disulfonate as well as benzene-1,3-disulfonate inhibit contraluminal35SO 4 2− influx (with an (app.K i of 〈6 mmol/l), while benzene-1,2- and 1,4-disulfonate do not. 2) The inhibitory potency of 1,3-benzene disulfonate is slightly augmented by an additional NH2 − or OH-group in position 4. However, OH-groups at position 4 and 5 or 4 and 6 abolish the inhibitory potency. 3) The naphthalene disulfonates tested inhibit only if they have an OH-group in ortho-position to one SO3H group. 4) The stilbene disulfonates H2DIDS and DNDS inhibit the contraluminal35SO 4 2− influx with high (app.K i≈0.8 mmol/l), DADS with lower potency (app.K i≈6 mmol/l). 5) Amongst the tested aliphatic di- and tricarboxylates inhibition was exerted by oxalate (app.K i 1.1 mmol/l) and maleate (app.K i 3.8 mmol/l), but not by malonate, hydroxymalonate and citrate. 6) Out of the tested benzenedicarboxylates only those inhibit which have the COO−-groups directly on the ring in 1,2 and 1,3 position (app.K i 4.0 and 2.7 mmol/l), but not in the 1,4 position. An additional OH-group in position 4 augments the inhibitory potency of 1,3 benzene-dicarboxylates (app.K i 0.8 mmol/l), while an OH group on position 5 abolishes it. 7) The benzene tricarboxylates (BTC) inhibit in the sequence 1,2,3-BTC〉1,3,5-BTC〉1,2,4-BTC (app.K i 0.9, 1.5 and 4.2 mmol/l, respectively). 8) The carboxy-benzene-sulfonates inhibit also in the 1,2 and 1,3 position only (app.K i 6.7 and 5 mmol/l), but not in the 1,4 position. Addition of an −OH-group to the 3-carboxy-1-benzene-sulfonate forming 4-hydroxy-3-carboxy-1-benzene-sulfate augments the inhibitory potency drastically (app.K i 0.32 mmol/l), while a NH2 substitution at the same position leaves it unchanged (app.K i 4.7 mmol/l). If, however, ethylamine instead of NH2 is used as substituent, the inhibitory potency is almost as high as of 4-hydroxy-3-carboxy-1-benzene-sulfonate (app.K i≈0.6 mmol/l). Amongst the dicarboxy-benzene-sulfonates, 3,4-carboxy-benzene-1-sulfonate inhibits (app.K i ca. 2 mmol/l), while 3,5-carboxy-benzene-1-sulfonate does not. The data indicate that a strong interaction of substrate with the sulfate transporter is given, when two charged groups (COO− and/or SO 3 − ) are present in a distance equivalent to the meta-position on the benzene ring and an additional hydrogen bond forming OH- or −NH-group. Hydrogen bond forming groups and charged groups in other positions usually abolish the inhibitory potency.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 407 (1986), S. 488-492 
    ISSN: 1432-2013
    Keywords: Lactate ; Pyruvate ; 3-hydroxybutyrate ; Acetoacetate ; Nonspecific anion channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the characteristic of contraluminal transport of hydrophylic small fatty acids the in situ stopped flow microperfusion technique [12] has been applied. By measuring with 4 s contact time the decrease in the contraluminal concentration of the respective radiolabelled substances the concentration dependence of the influx into the cortical cells was tested. The 4 s decrease in contraluminal concentration of chloroacetate,l-lactate,d-lactate, 3-hydroxybutyrate and acetoacetate was between 26% and 31%. For each substance the percent decrease was the same, no matter whether it was offered in a concentration of 0.1 or 10 mmol/l. Contraluminal disappearance of 0.1 mmol/ll-lactate was not influenced by 5 mmol/l H2DIDS, probenecid, phloretin, mersalyl or cyanocinnamate, but it was significantly (37%) inhibited by 5-nitro-2-(phenyl-propyl-amino) benzoate, a blocker of the nonspecific anion channel. The percent decrease in propionate uptake was somewhat larger — between 36% and 39% — but again not different at 0.01, 0.1, 1.0 and 10 mmol/l. With pyruvate the contraluminal decrease was 20% at 0.1 mmol/l and 31% at 10 mmol/l. The percent disappearance of the aromatic pyrazinoate was 38% and 34% at 0.1 and 10 mmol/l and for nicotinate 42% and 22%, respectively. The disappearance of nicotinate (0.1 mmol/l) was significantly inhibited by 10 mmol/l pyrazinoate and paraaminohippurate (PAH). The data are in agreement with the hypothesis that the hydrophilic small fatty acids traverse the contraluminal cell side by simple diffusion, possibly via the unspecific anion channel [14], pyruvate via the dicarboxylic acid pathway in a cooperative manner and pyrazinoate, as well as nicotinate, via the PAH pathway.
    Type of Medium: Electronic Resource
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