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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.
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  • 2
    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.
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  • 3
    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.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 404 (1985), S. 307-310 
    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 of the contraluminal sulfate transport system the inhibitory potency of salicylate analogs (5 mmol/l each) on the35SO 4 2− influx from the interstitium into cortical tubular cells in situ has been determined. The following was found: 2-hydroxybenzoate (salicylate), per se, did not inhibit contraluminal35SO 4 2− influx. The same holds when an additional NH2-group was introduced in position 4 or 5, or when an additional Cl-group was introduced in position 4. When an additional Cl- or NO2-group was introduced in position 5 a moderate inhibition was seen (app.K i≈4 mmol/l). However, introduction of 2 Cl- or 2 NO2-groups in position 3 and 5 creates compounds with strong inhibitory potency (app.K i≈0.5 mmol/l). 2-hydroxy-3,5-iodobenzoate inhibited too, but with a smaller inhibitory potency (app.K i≈2.3 mmol/l). 2-hydroxybenzoate analogs, which have a carboxy- or sulfo-group in position 5, exerted strong inhibition, those with a acetyl- or butyryl-group exerted moderate inhibition. 1-Naphthol-2-carboxylate did not inhibit, while 1-naphthol-4-sulfamoyl-2-carboxylate did. Amongst the dihydroxybenzoates, 2,3- and 2,5-dihydroxybenzoate did not inhibit contraluminal35SO 4 2− influx, while 2,4- and 2,6-dihydroxybenzoate did. The data indicate that a hydroxy-group in ortho-position and an electro-negative group in the meta-position to the carboxyl group and paraposition to the hydroxy-group are essential for interaction with the contraluminal sulfate transport system. The ability of 2,6-dihydroxybenzoate to inhibit might be explained by its ability to undergo mesomeric conformation.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 404 (1985), S. 311-318 
    ISSN: 1432-2013
    Keywords: Epithelial transport ; Contraluminal cell membrane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to evaluate the specificity for the contraluminal sulfate transport system the inhibitory potency of phenol- and sulfonphthaleins, of sulfamoyl-compounds (diuretics) as well as diphenylamine-2-carboxylates (Cl− channel blockers) on the35SO 4 2− influx from the interstitium into cortical tubular cells in situ has been determined. The following was found: 1) Phenolsulfonphthalein (phenol-red) inhibited with an app.K i-value of 1.7 mmol/l, while analogs which had additional Br-atoms in position 3 and/or 5, i.e. bromphenol-blue, bromcresol-purple and bromcresol-green, inhibited with an apparentK i of 0.1 and 0.5 mmol/l respectively. 2) Phenolphthalein and tetrabromphenolphthalein did not inhibit, while the disulfonate dyes bromsulfalein, fuchsin acid and indigocarmine inhibited with aK i between ≈1 and 3 mmol/l. The highest inhibitory potency in this class of compounds was seen with orange G (app.K i 0.07 mmol/l). The monosulfonate dyes tested, fluoresceinsulfonate and orange I inhibited moderately with an app.K i of ≈5 mmol/l. 3) The 3-sulfamoyl compounds inhibited to a varying degree, when they had a neighbouring −NH-group (furylmethylamino-group), i.e. in position 6 to the COOH or SO3H-group, or when they had a phenoxy-group in position 4. 4) 4-sulfamoylbenzoate and the related compounds probenecid, acetazolamide and hydrochlorothiazide inhibited with an app.K i between 4 and 7 mmol/l. 5) All diphenylamine-2-carboxylate analogs inhibited with an app.K i between 3 and 5 mmol/l, even when the −NH-group was replaced by an =O-group or the benzene ring was replaced by a pyrimidine ring, but not when it was replaced by a thiophen ring. In contrast, 4-phenylaminepyridine-3-sulfonate was ineffective, while diphenylamine-2-amino sulfonate exerted the highest inhibition of this group with an app.K i of 1.4 mmol/l. When, however, the aminosulfonate group was replaced by a methylsulfonamide, the inhibitory potency disappeared. The data can be explained by inhibitory patterns found in previous papers for disulfonates [29], sulfonates with a hydrophobic moiety [28] or neighbouring OH-group [28, 29], carboxylates with a neighbouring −NH- or OH-group in position 2- and an electron-attracting group in position 5 [30].
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 413 (1988), S. 134-146 
    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.
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  • 7
    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.
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  • 8
    ISSN: 1432-2013
    Keywords: Oxalate ; Succinate ; Glutarate ; 2-Oxoglutarate ; Citrate ; Sulfate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the specificity for contraluminal para-aminohippurate (PAH) transport, the inhibitory potency of aliphatic dicarboxylates on3H-PAH influx, as well as the inhibitory effect on35SO 4 2− - and3H-succinate influx, from the interstitium into cortical tubular cells in situ has been determined. The following was found: 1. Testing a homologous series of dicarboxylates-ranging from the 2 C oxalate to the 10 C sebacate — PAH transport was inhibited by succinate (app.K i 1.35 mmol/l), and all longer dicarboxylates, with high potency (app.K i 0.05–0.35 mmol/l). Sulfate transport was inhibited only by oxalate (app.K i 1.1 mmol/l), while dicarboxylate transport was inhibited by succinate, glutarate, adipate and pimelate with decreasing potency (app.K i 0.04, 0.24, 0.91, 4.0 mmol/l, respectively). 2. PAH transport was inhibited by succinate and glutarate with high potency (app.K i 1.35 and 0.05 mmol/l), by the correspondent monomethylester to a lesser extent (app.K i 1.7 and 0.74 mmol/l), but not by the dimethylester. On the other hand, the semialdehyde of succinate with aK i-value of 1.2 mmol/l, had the same inhibitory potency as succinate itself, while the dialdehyde of glutarate (app.K i 1.4 mmol/l) was much less potent as glutarate. 3. Introduction of an oxo-, methyl- or sulfhydroxylgroup onto the 2-position of succinate, or of an oxo-group onto the 2-position of glutarate moderately augmented the inhibitory potency against PAH-uptake. However, introduction of a 2-hydroxy group onto succinate or glutarate in thel-position reduced the inhibitory potency more than in thed-position. Introduction of two methyl-, sulfhydryl- or hydroxyl-groups in the 2–3-position of succinate reduced or abolished its inhibitory potency. The introduction of a 2-amino group onto succinate or glutarate abolished its effect on PAH transport. However, N-acetylation or N-benzoylation led to a restitution in inhibitory potency. 4. The trans-isomers fumarate and mesaconate inhibited PAH- and methylsuccinate transport, while the cis-isomers maleate and citraconate did so to a lesser extent or not at all. The effect was reversed with the tricarboxylic aconitates, because cis-aconitate bears a CH2-extended COOH-group in trans-position and trans-aconitate in cis-position. The data indicate that there exist three different anion transport systems at the contraluminal cell side of the proximal renal tubule: 1. a sulfate-oxalate transporter, 2. a sodium-dependent dicarboxylate transporter, and 3. a paraaminohippurate transporter. The PAH transport system accepts dicarboxylates with chain length higher than 7.5 Å (=distance between the terminal oxygen atoms), while the dicarboxylate transport interacts with dicarboxylates with a chain length between 6.5 and 10 Å. Both transport systems prefer the transconfiguration. The effect of side groups on the interaction of dicarboxylates with the PAH-transport system is due mainly to hydrophobicity and electron configuration.
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  • 9
    ISSN: 1432-2013
    Keywords: 2-Oxoglutarate ; Lactate ; Pyruvate ; Nitrate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract In order to study the characteristics of contraluminal para-aminohippurate transport into proximal tubular cells the stopped flow capillary perfusion method was applied. The disappearance of3H-paraaminohippurate from the capillary perfusate at different concentrations and contact times was measured and saturation type behaviour was found with aK m of 0.08±0.01 (SE) mmol/l,J max of 1.1±0.1 pmol·s−1·cm−1 andr, the final extracellular/intracellular distribution ratio of 0.93±0.03. Omission of Na+ from the capillary test perfusate caused a small reduction of contraluminal PAH uptake at small transport rates (0.1 mmol/l PAH in the test perfusate) but not at high transport rates (1.0 mmol/l PAH in the test perfusate). Change of K+ between 0 and 40 mmol/l and pH between 6.0 and 8.0 did not influence contraluminal PAH uptake. Isotonic replacement of chloride by gluconate, nitrate, sulfate, phosphate, methanesulfonate or increase in bicarbonate to 50 mmol/l did not influence PAH uptake at small transport rates. But isotonic sulfate and phosphate, as well as 50 mmol/l HCO 3 − and 25 mmol/l Hepes in isotonic solutions reduced PAH uptake at high transport rates. Addition of 5 mmol/l Ca2+, Mg2+, Mn2+, Ba2+, Cd2+ to isotonic Na+-gluconate solution did not influence PAH uptake except for Mg2+ and Mn2+ which inhibited uptake at small transport rates only. Preperfusion of the peritubular capillaries with rat serum, Na+ gluconate (Ca2+-+Mg2+-free), Na+ gluconate (Ca2+-+Mg2+-free) plus 10 mmol/l lactate or pyruvate or 0.1 mmol/l 2-oxoglutarate did not influence PAH uptake at small PAH transport rates, but inhibited at high transport rates. Preperfusion of the capillaries for 10 s with Na+-, Ca2+- and Mg2+-free solutions reduced PAH uptake in the presence of Na+ at both transport rates. A second 10 s preperfusion — after the first 10 s Na+-, Ca2+-, Mg2+-free preperfusion — with serum or solutions which contained Na+ and Ca2+ or Mg2+ restored the PAH fluxes to control values. The data are compatible with the hypothesis that contraluminal PAH uptake occurs by a saturable transport mechanism in exchange for other intracellular anions rather than in cotransport with Na+ ions. It was, however, not possible to identify the type of counteranions involved. The large effect of cation replacement on para-aminohippurate transport, which was reported in many previous studies with kidney slices, is not a direct effect on the para-aminohippurate transporter, but is rather caused indirectly via cell metabolism and/or changed ion gradients.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 409 (1987), S. 547-554 
    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.
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