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  • 1
    Electronic Resource
    Electronic Resource
    Contraluminal para-aminohippurate (PAH) transport in the proximal tubule of the rat kidney (1988)
    Springer
    Pflügers Archiv 413 (1988), S. 134-146 
    Details
    ISSN: 1432-2013
    Keywords: Organic anion transport ; Sulfate transport ; Dicarboxylate transport ; Phenolate transport ; Salicylate transport ; Cinnamate transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the specificities of the contraluminal anion transport systems, the inhibitory potency of substituted benzene analogs on influx of [3H]PAH, [14C]succinate, and [35S]sulfate from the interstitium into cortical tubular cells has been determined in situ: (1) Contraluminal [3H]PAH influx is moderately inhibited by benzene-carboxylate and benzene-sulfonate, and strongly by benzene-dicarboxylates,-disulfonates and carboxy-benzene-sulfonates, if the substituents are located at positions 1 and 3 or 1 and 4. The affinity of the PAH transporter to polysubstituted benzoates increases with increasing hydrophobicity, decreasing electron density at the carboxyl group and decreasing pKa. Similar dependencies are observed for phenols. Benzaldehydes which do not carry an ionic negative charge are accepted by the PAH-transporter, if they possess a second partially charged aldehyde or NO2-group. (2) Contraluminal [14C]succinate influx is inhibited by benzene 1,3- or 1,4-dicarboxylates,-disulfonates and 1,3-or 1,4-carboxybenzene-sulfonates. Monosubstituted benzoates do not interact with the dicarboxylate transporter, but NO2-polysubstituted benzoates do. Phenol itself and 2-substituted phenol interact weakly possibly due to oligomer formation. (3) The contraluminal sulfate transporter interacts only with compounds which show a negative group accumulation such as 3,5-dinitro- or 3,5-dichloro-substituted salicylates. The data are consistent with three separate anion transport systems in the contraluminal membrane: The PAH transporter interacts with hydrophobic molecules carrying one or two negative charges (−COO−, −SO 3 − ) or two or more than two partial negative charges (−OH, −CHO, −SO2NH2, −NO2). The dicarboxylate transporter requires two electronegative ionic charges (−COO−, −SO 3 − ) at 5–9 Å distance or one ionic and several partial charges (−Cl, −NO2) at a favourable distance. The sulfate transporter interacts with molecules which have neighbouring electronegative charge accumulation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582523
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  • 2
    Electronic Resource
    Electronic Resource
    Contraluminal para-aminohippurate transport in the proximal tubule of the rat kidney (1987)
    Springer
    Pflügers Archiv 409 (1987), S. 547-554 
    Details
    ISSN: 1432-2013
    Keywords: Dicarboxylate transport ; Sulfate transport ; Benzoyl compounds ; Phenoxy compounds ; Valproate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the specificity of the contraluminal para-aminohippurate (PAH) transport system, the inhibitory potency of monocarboxylates on the3H-PAH influx from the interstitium into cortical tubular cells in situ has been determined. The following was found: if a homologous series of fatty acids with increasing chain length is tested, inhibition of contraluminal PAH influx is first seen with valerate (app.K i 1.4 mmol/l), increasing up to nonanoate (app.K i 0.06 mmol/l) and remaining in this range up to duodecanoate, the last compound of this series which is sufficiently water-soluble. Similarly, the inhibitory potency of aromatic monocarboxylates increases with increasing hydrophobicity. If the fatty acids are esterified, their inhibitory potency is lost. If they are transformed to the respective aldehydes their inhibitory potency is preserved at a reduced degree. Introduction of a hydrophobic methyl-, ethyl-, or propyl-group increases the inhibitory potency. A β-, but not an α-oxo-group augments the inhibitory potency of phenylpropionate analogs, an OH group diminishes it, and a NH2 group abolishes it. Among phenyl-fatty acids an increase in affinity is observed from phenyl- 〈 benzoylamine-〈 phenoxy- 〈 benzoyl-acetate and-propionate. All monocarboxylate compounds, so far tested, do not inhibit contraluminal sulfate and Na+/succinate influx. The data indicate that the PAH transporter interacts with monocarboxylates and also with aldehydes which have a hydrophobic moiety. An additional oxo-group facilitates the interaction. Thus, the benzoyl compounds show the highest affinity observed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584652
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  • 3
    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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  • 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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  • 5
    Electronic Resource
    Electronic Resource
    Bicarbonate reabsorption in the papillary collecting duct of rats (1981)
    Springer
    Pflügers Archiv 389 (1981), S. 271-275 
    Details
    ISSN: 1432-2013
    Keywords: Adaptation, HCO 3 − transport ; Glycodiazine transport ; Metabolic acidosis ; Metabolic alkalosis ; Acetazolamide ; SITS ; Potassium deficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Using the technique of capillary perfusion and simultaneous luminal stop flow microperfusion the reabsorption of bicarbonate and glycodiazine from the papillary collecting duct was evaluated. Starting with equal H14CO 3 − and3H-glycodiazine concentrations in the luminal and peritubular perfusates, the decrease in the luminal concentration at 10 and 45 s contact time was measured. In control rats with 25 mmol/l HCO 3 − in the perfusates the rate of HCO 3 − reabsorption calculated from the 10 s values was 0.34 nmol cm−2s−1. In acute metabolic acidosis, the rate of bicarbonate reabsorption was 2,3 times higher. In metabolic alkalosis, the rate of bicarbonate absorption dropped to 13% of the control values. Also the 45 s values of acidotic and alkalotic animals differed significantly from each other. With 25 mmol/l glycodiazine in both perfusates the rate of biffer reabsorption as calculated from the 10 s values was 0.76 nmol cm−2s−1 in control rats and did not deviate significantly from this value in acidotic and alkalotic animals. In control rats the bicarbonate reabsorption in % was the same, no matter whether both luminal and capillary perfusate contained 25 mmol/l bicarbonate or 10 mmol/l. In acidotic rats the rate of HCO 3 − reabsorption did not change significantly if all Na+ in the perfusates was replaced by choline (0.88 versus 0.79 nmol cm−2s−1 at 25 mmol/l HCO 3 − ). When in acidotic rats 0.1 mmol/l acetazolamide or 1 mmol/l SITS (4-acetamido-4′-isothiocyanatostilbene-2,2′-disulfonic acid) was added to both perfusates the rate of HCO 3 − reabsorption dropped by 75 and 58%, respectively. A potassium deficient diet for one week and DOCA administration had no influence on the bicarbonate reabsorption of rats which were on standard diet. The data indicate that (1) the buffer reabsorption from the papillary collecting duct is rather due to H+ ion secretion than to buffer anion reabsorption. (2) The adaptation to metabolic acidosis and alkalosis is specific for bicarbonate and not seen with glycodiazine. (3) Within the concentration range tested the HCO 3 − reabsorption rises linearly with the HCO 3 t- concentration. (4) The HCO 3 − reabsorption in the papillary collecting duct is Na+-independent, it can be inhibited by acetazolamide and SITS, but is not influenced by K+-deficient diet plus DOCA.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584789
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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    Coupling between proximal tubular transport processes (1977)
    Springer
    Pflügers Archiv 368 (1977), S. 245-252 
    Details
    ISSN: 1432-2013
    Keywords: Renal tubule ; H+ ion secretion ; Na+ coupled transport ; Ouabain ; SITS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The rate of active transport by the proximal renal tubule of amino acid (l-histidine), sugar (α-methyl-d-glycoside), H+ ions (glycodiazine), phosphate and para-aminohippurate was evaluated by measuring the zero net flux concentration difference (Δc) of these substances. In the case of calcium the electrochemical potential differenceΔc +zFci Δϕ/RT) was the criterion employed. The rate of isotonic Na+-absorption (JNa) was measured with the shrinking droplet method. The effect of ouabain on the transport of these substances was tested in the golden hamster and the effect of SITS (4-acetamido-4′isothiocyanatostilbene 2,2′-disulfonic acid) was observed in rats. Ouabain (1 mM) applied peritubularly incompletely inhibited JNa (80%), but in combination with acetazolamide (0.2 mM) the inhibition was almost complete (93%). In addition, ouabain inhibited the sodium coupled (secondary active) transport processes ofl-histidine, α-methyl-d-glycoside, calcium and phosphate by more than 75%. It did not affect H+ (glycodiazine) transport and PAH transport was only slightly affected. When SITS (1 mM) was applied from both sides of the cell it inhibited H+ (glycodiazine) transport by 72% and reduced JNa by 38% when given from only the peritubular cell side. SITS (1 mM), however, had no significant affect on H+ secretion and sodium reabsorption if it was applied from only the luminal side. Furthermore it had no affect on the other transport processes tested, regardless of the cell side to which it was applied. When the HCO 3 − buffer or physically related buffers were omitted from the perfusate the absorption of Na+ was reduced by 66%, phosphate by 44%, andl-histidine by 15%. All the other transport processes tested were not significantly affected. The data are consistent with the hypothesis that the active transport processes of histidine, α-methyl-d-glycoside and phosphate, which are located in the brush border, are driven by a sodium gradient which is abolished by ouabain. This may also apply to the Na+-Ca2+ countertransport located at the contraluminal cell side. The residual Na+ transport remaining in the presence of ouabain is likely to be passively driven by the continuing H+ transport which probably is driven directly by ATP. SITS seems to inhibit the exit step of HCO 3 − from the cell and secondary to that, the luminal H+-Na+ exchange and consequently the Na+ reabsorption. In the absence of HCO 3 − buffer in the perfusates the luminal H+-Na+ exchange seems to be affected and the pattern of inhibition of the other transport processes is almost the same as with SITS. The different effects onP i reabsorption observed under these conditions might be explained by possible variations in intracellular pH.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585203
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