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  • 1980-1984  (4)
  • Renal tubule  (3)
  • Cinnamate  (1)
  • Phosphate transport
  • 1
    Electronic Resource
    Electronic Resource
    Reabsorption of monocarboxylic acids in the proximal tubule of the rat kidney (1982)
    Springer
    Pflügers Archiv 395 (1982), S. 212-219 
    Details
    ISSN: 1432-2013
    Keywords: SITS ; Probenecid ; Phloretin ; Acetazolamide ; Lactate ; Renal tubule
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The transport ofd-lactate across the epithelium of the late proximal convolution was investigated by two methods: 1. by measuring the zero net flux transtubular concentration difference (Δc tt,45s) and the permeability (P) ofd-lactate and calculating from both the transtubular active transport rate (J lac act ). 2. By measuring the 3.5 s efflux ofd-lactate from the tubular lumen, while blood was flowing through the capillaries. The 3.5 s efflux comprises two components, one going through the brush border (J lac bb ) and one going the paracellular pathway (J lac paracell =P lac·c lac lumen). Both,J lac act andJ lac bb ofd-lactate gave the sameK m 1.9 and 1.7 mmol/l and the same maximal transport rate 3.2 and 2.9 pmol cm−1 s−1. TheK i ofl-lactate tested againstJ lac act andJ lac bb ofd-lactate was also the same: 1.1 and 1.0 mmol/l. These data indicate that under our experimental conditions only the flux through the brush border seems to be rate limiting and thatd-lactate uses the same transport system asl-lactate. When Na+ was omitted from the perfusatesJ lac act disappeared completely, whileJ lac bb was reduced by 64%. These data reflect the Na+ dependence of thed-lactate transport through the brush border. Variation of intra-and extracellular pH by raisingpCO2, omitting HCO 3 − from the perfusates or adding acetazolamide had no effect on the transport ofd-lactate when α-ketoglutarate was used as fuel. However, when acetate was used as fuel, intracellular acidosis brought the reducedJ lac act back to the values obtained with α-ketoglutarate as fuel. It is suggested that this is an effect on a contraluminal transport step. Probenecid (5 mmol/l) and phloretin (0.25 mmol/l) inhibitedJ lac act significantly.J lac bb , however, was only inhibited by probenecid when acetate was used as fuel. These data indicate that both compounds act on thed-lactate exit at the contraluminal cell side, but that probenecid acts in addition at the luminal cell side. SITS (1 mmol/l) augmentedJ lac bb when acetate was used as fuel and is similar to the effect of lowering intracellular pH as described above. The SH reagents mersalyl (1.0 mmol/l) and maleolylglycine (1 mmol/l) did not influenceJ lac bb .
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584812
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Active sulfate reabsorption in the proximal convolution of the rat kidney: Specificity, Na+ and HCO 3 − dependence (1980)
    Springer
    Pflügers Archiv 383 (1980), S. 159-163 
    Details
    ISSN: 1432-2013
    Keywords: Renal tubule ; Sulfate transport ; Na+ coupled transport ; Thiosulfate ; Molybdate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using the standing droplet technique in the proximal convolution and simultaneous microperfusion of the peritubular capillaries, the decrease in luminal sulfate concentration with time and the zero net flux transtubular concentration difference of sulfate ( $$\Delta c_{{\text{SO}}_{\text{4}}^{{\text{2 - }}} } $$ ) at 45 s was determined — the latter being taken as a measure of the rate of active sulfate reabsorption. Starting with 0.5 mmol/l sulfate in both perfusates the $$\Delta c_{{\text{SO}}_{\text{4}}^{{\text{2 - }}} } $$ value of 0.35 mmol/l was approached exponentially with a half value time of 4.3 s. The $$\Delta c_{{\text{SO}}_{\text{4}}^{{\text{2 - }}} } $$ values in the early proximal and late proximal convolution did not deviate from each other. If the Na+ concentration in the perfusates was reduced, the $$\Delta c_{{\text{SO}}_{\text{4}}^{{\text{2 - }}} } $$ approached zero and extrapolated to a slightly negative value (c i〉c o). When 1 mmol/l ouabain was added to the perfusates $$\Delta c_{{\text{SO}}_{\text{4}}^{{\text{2 - }}} } $$ decreased by 66% (the latter experiments were performed in the golden hamster which is more sensitive to ouabain than the rat). 1 mmol/l thiosulfate diminished $$\Delta c_{{\text{SO}}_{\text{4}}^{{\text{2 - }}} } $$ by 68% and 1 mmol/l molybdate by 24%. Omitting or replacing bicarbonate by HEPES or glycodiazine reduced the sulfate reabsorption significantly, while acetazolamide (0.1 mmol/l) and increasing the CO2-pressure from 4.66 to 14.0 kPa (i.e. 5–15% CO2) had no effect. SITS 1 mmol/l had no effect on sulfate reabsorption. The data indicate that the sulfate reabsorption is driven by a Na+ gradient and inhibited by thiosulfate and molybdate, i.e. molecules which have a similar tetrahedral molecule structure. The sulfate reabsorption depends in an undefined manner on the presence of bicarbonate ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581877
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    Paper (German National Licenses)
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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
    Bidirectional active transport of thiosulfate in the proximal convolution of the rat kidney (1980)
    Springer
    Pflügers Archiv 387 (1980), S. 127-132 
    Details
    ISSN: 1432-2013
    Keywords: Renal tubule ; Thiosulfate transport ; Na+ coupled transport ; Sulfate transport ; Paraaminohippurate transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using the standing droplet method in the late proximal convolution and simultaneous microperfusion of the peritubular capillaries, the zero net flux transtubular concentration difference of thiosulfate at 45 s was determined, the latter being taken as a measure of active thiosulfate transport. Under control conditions, in the presence of Na+, near zero Δc values were observed. When 1 mmol/l carinamide or paraaminohippurate (PAH) were added to the perfusates significant reabsorptive Δc arose. However, when 7.5 mmol/l sulfate was added to the Na+-free secretory Δc values were observed. Tested under Na+-free conditions, the secretory Δc was not influenced by simultaneously present 5 mmol/l of SO 4 2− but was diminished by 50 mmol/l SO 4 2− . PAH (1 mmol/l), carinamide (0.2 mmol/l) and probenecid (1 mmol/l) decreased the secretory Δc by 48, 65 and 48%, respectively. The PAH secretion was not influenced, when thiosulfate or sulfate up to 50 mmol/l was added to both perfusates. Under Na+-free conditions the Δc of thiosulfate in early loops of the proximal convolution is higher than in late loops, while for PAH this pattern is reversed. Taken together with the previously published inhibition of sulfate reabsorption by thiosulfate the data indicate 1. thiosulfate is reabsorved by the Na+-dependent sulfate transport system and 2. thiosulfate is simultaneously secreted by a carinamide-, probenecid-and PAH-sensitive secretory system. The secretory system might also be shared by sulfate. The thiosulfate net flux is the result of the difference in the activity of the counteracting transporters, located at the luminal and contraluminal cell side. Is is possible that the higher activity of the transporter at one cell side leads to a reversal of the flux through the transporter at the other cell side.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584263
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    Paper (German National Licenses)
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