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  • 1980-1984  (4)
  • Cinnamate  (1)
  • Citrate-transport  (1)
  • Contraluminal cell membrane  (1)
  • Electrolyte transport  (1)
  • Epithelialer Transport  (1)
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Material
Years
Year
Keywords
  • 1
    Electronic Resource
    Electronic Resource
    Transport of inorganic and organic substances in the renal proximal tubule (1982)
    Springer
    Journal of molecular medicine 60 (1982), S. 1165-1172 
    Details
    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
    URL: http://dx.doi.org/10.1007/BF01716718
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  • 2
    Electronic Resource
    Electronic Resource
    Contraluminal sulfate transport in the proximal tubule of the rat kidney (1984)
    Springer
    Pflügers Archiv 402 (1984), S. 264-271 
    Details
    ISSN: 1432-2013
    Keywords: Epithelial transport ; Contraluminal cell membrane ; Anion exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study contraluminal sulfate transport the influx rate of35SO 4 2− from the interstitium into cortical tubular cells has been determined. Preloading of the rat with sulfate augmented contraluminal35SO 4 2− influx; preperfusion with sulfate-free solutions diminished it. The contraluminal35SO 4 2− influx in sulfate-loaded animals followed two parameter kinetics (K m 1.4 mmol/l,J max 1.2 pmol·s−1·cm−1). The contraluminal35SO 4 2− influx (starting concentration 10 μmol/l) did not change when the K+ concentration was varied between 4 and 40 mmol/l and the Ca2+ concentration from zero to 3 mmol/l. Omission of Na+ from the perfusates augmented contraluminal35SO 4 2− influx markedly. The increase is larger at pH 6 than at pH 7.4. Changes of pH affect contraluminal35SO 4 2− influx only when the solutions are Na+- and K+-free. Under these conditions the35SO 4 2− influx decreased when the ambient pH was raised from pH 6.0 to pH 8.0. Thiosulfate, selenate, molybdate, oxalate, phosphate, arsenate, and bicarbonate exerted competitive inhibition, while formate, 2-oxoglutarate and paraaminohippurate showed a biphasic response: inhibition at 50 mmol/l, no inhibition at 150 mmol/l. Chloride and bicarbonate inhibited35SO 4 2− influx at 10 μmol/l35SO 4 2− , but augmented sulfate influx at 5 mmol/l35SO 4 2− concentration in rats not preloaded with sulfate. The data indicate the presence of a contraluminal sulfate transport system which is shared by a variety of inorganic and organic anions. The biphasic behaviour of some anions suggests parallel pathways leading to a cis-inhibition at small and trans-stimulation at high anion concentrations. Na+ and H+ may be cotransported or interact with the transport system at a modifier site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585509
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  • 3
    Electronic Resource
    Electronic Resource
    Reabsorption of monocarboxylic acids in the proximal tubule of the rat kidney (1982)
    Springer
    Pflügers Archiv 395 (1982), S. 227-231 
    Details
    ISSN: 1432-2013
    Keywords: d-Lactate ; Benzoate ; Cinnamate ; Nicotinic acid ; Pyrazinoate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The 3.5 s efflux ofd-lactate (1 mmol/l) injected in the lumen of the late proximal convolution was measured. This efflux can be divided into a Na+-dependent, saturable component flowing through the brush border and a Na+-independent non-saturable component flowing through the paracellular pathway. The inhibitory potency of benzoate and its analogs, of phenyl-substituted acetate-, propionate-and butyrate analogs, of cinnamate and analogs, of heterocyclic monocarboxylic acids and related compounds added to the perfusate in a concentration of 10 mmol/l was measured. It was found that 1. benzoate added in a concentration of 10 mmol/l to the luminal perfusate inhibits transport ofd-lactate, and the meta- and para-substituted analogs of benzoate inhibit in a fashion predicted by Hammett's theory. Side groups which withdraw electrons from the COOH group inhibit while substitutes who deliver electrons toward the reaction center do not. 2. Replacement of a hydrogen atom by a phenyl ring at the C2 atom of acetate, glycolate and glyoxylate does not change the inhibitory pattern of these substances ond-lactate transport. Replacement of a hydrogen atom on the C2 atom of propionate and lactate reduces the ability of these molecules to inhibitd-lactate transport. But replacement of a hydrogen atom at the C3 atom of propionate, pyruvate and lactate abolishes the inhibitory potency. Similarly the inhibitory potency decreases from butyrate 〉 2-phenylbutyrate 〉 3-phenylbutyrate 〉 4 phenylbutyrate. The latter two are actually no longer inhibitory. 3. Trans-cinnamate, cis-cinnamate (3-phenyl trans or cis acrylic acid) and 3-phenylpropiolate are also not inhibitory. But introduction of an electron attracting CN group on C2 atom of cinnamate evokes inhibitory potency. 4. The heterocyclic compounds nicotinic acid and pyrazinoic acid exert strong inhibition ond-lactate transport, while picolinic acid and isonicotinic acid exert only moderate inhibition. Nicotinic and pyrazinoic acid show also a secretory component in their transport behaviour. 5. If the COOH group of benzoate is replaced by a SO3H group (benzenesulfonic acid) or if a second ring is induced (1 or 2 naphthoic acid) the inhibitory potency is lost. 6. Amongst other organic anions which do not inhibitd-lactate transport are paraaminohippurate, urate, and taurocholate. The data indicate that a main determinant of the specificity of the Na+-dependent aliphatic aromatic monocarboxylic acid reabsorption system in the renal brush border is the electron density at the reaction center, i.e. the free carboxylic group. Furthermore, the size of the molecule and its hydrophobicity at one cell pole is limiting for its ability to react with the carrier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584814
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  • 4
    Electronic Resource
    Electronic Resource
    Secretion and contraluminal uptake of dicarboxylic acids in the proximal convolution of rat kidney (1984)
    Springer
    Pflügers Archiv 400 (1984), S. 241-249 
    Details
    ISSN: 1432-2013
    Keywords: Basolateral cell membrane ; Methylsuccinate-transport ; 2-Oxolutarate-transport ; Citrate-transport ; Lithium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The transport of dicarboxylic acids in the proximal convolution was investigated by measuring: a) the zero net flux transtubular concentration difference ofdl-methyl-succinate, b) its 2-s influx from the interstitium into tubular cells, and c) its 3.5-s efflux from the tubular lumen. With the first method a luminal concentration exceeding the peritubular concentration was observed, thus indicating a net active transtubular secretion of this slowly metabolized substance. All transport steps, luminal and contraluminal, as well as the overall transport, were Na+-dependent and inhibited by lithium (apparentK i ≈ 1.8 mmol/l). The overall transport of methylsuccinate, as well as the contraluminal influx into proximal tubular cells, could be inhibited by paraaminohippurate and H2-DIDS with an apparentK i of ≈ 1.8 mmol/l, by taurocholate with an apparentK i ≈ 3.` mmol/l and by pyruvate with an apparentK i ≈ 5 mmol/l, but not by sulfate, thiosulfate,l-lactate, oxalate and urate. As judged from the inhibition of contraluminal methylsuccinate influx by 48 dicarboxylic acids (aliphatic and aromatic), a specificity pattern was observed similar to that of inhibition of luminal efflux of 2-oxoglutarate [22]: a preference of dicarboxylates in the transconfiguration with a chain length of 4–5 carbons; little change in the inhibitory potency with CH3 −, OH−, SH−and O=, but strong reduction with a NH 3 + in the 2 position; only a small reduction of inhibitory potency with 2,3 disubstituted SH and OH analogs; preference of the dicarboxylic benzene in the 1,4 position and of the diacetyl benzene in the 1,2 position. The data indicate a Na+-dependent dicarboxylic transport system at the contraluminal cell side of the proximal tubule which is very similar to the luminal transport system for dicarboxylic acids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581554
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    Paper (German National Licenses)
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