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  • 1985-1989  (6)
  • Cl−-channel  (3)
  • Diphenylamine-2-carboxylate  (2)
  • Mouse kidney  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Cl−-channels in the apical cell membrane of the rectal gland “induced” by cAMP (1985)
    Springer
    Pflügers Archiv 403 (1985), S. 446-448 
    Details
    ISSN: 1432-2013
    Keywords: Cl−-secretion ; Cl−-channel ; K+-channel ; CAMP mediated secretion ; patch clamp method ; rectal gland of shark
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Isolated rectal gland tubules (n≈1000) of dogfish (Squalus Acanthias) were perfused in vitro. Individual channels in the apical and basolateral cell membrane were recorded with the patch clamp method. K+-channels were present in excised membrane patches of the basolateral membrane in stimulated (dbcAMP + forskolin + adenosine) and in nonstimulated state. Cl−-channels were found only in patches of the apical cell membrane when the tubule was stimulated. Cell attached recordings and simultaneous transepithelial PD measurements were obtained while the segment was stimulated. It is shown that concomitant with the increase in lumen negative PD “silent” membrane patches of the apical cell membrane suddenly develop Cl−-channel activity. It is concluded that stimulation of rectal gland tubules “activates” Cl−-channels in the apical cell membrane.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00589260
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  • 2
    Electronic Resource
    Electronic Resource
    Differential effects of ADH on sodium, chloride, potassium, calcium and magnesium transport in cortical and medullary thick ascending limbs of mouse nephron (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 516-523 
    Details
    ISSN: 1432-2013
    Keywords: ADH ; Transepithelial ion net fluxes ; Na+, Cl−, K+, Ca2+ and Mg2+ transport ; Electron microprobe ; Mouse kidney ; Cortical and medullary thick ascending limb of Henle's loop ; In vitro microperfusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effect of antidiuretic hormone (arginine vasopressin, AVP) on transepithelial Na+, Cl−, K+, Ca2+ and Mg2+ net transports was investigated in medullary (mTAL) and cortical (cTAL) segments of the thick ascending limb (TAL) of mouse nephron, perfused in vitro. Transepithelial net fluxes (J Na +,J Cl −,J K +,J Ca 2+,J Mg 2+) were determined by electron probe analysis of the collected tubular fluid. Transepithelial potential difference (PDte) and transepithelial resistance (Rte) were measured simultaneously. cTAL segments were bathed and perfused with isoosmolal, HCO 3 − containing Ringer solutions, mTAL segments were bathed and perfused with isoosmolal HCO 3 − free Ringer solutions. In cTAL segments, AVP (10−10 mol·l−1) significantly increasedJ Mg 2+ andJ Ca 2+ from 0.39±0.08 to 0.58±0.10 and from 0.86±0.13 to 1.19±0.15 pmol·min−1 mm−1 respectively. NeitherJ Na + norJ Cl −, (J Na +: 213±30 versus 221±28 pmol·min−1 mm−1,J Cl −: 206±30 versus 220±23 pmol·min−1 mm−1) nor PDte (13.4±1.3 mV versus 14.1±1.9 mV) or Rte (24.6±6.5Ω cm2 versus 22.6±6.4Ω cm2) were significantly changed by AVP. No significant effect of AVP on net K+ transport was observed. In mTAL segments, Mg2+ and Ca2+ net transports were close to zero and AVP (10−10 mol·l−1) elicited no effect. However NaCl net reabsorption was significantly stimulated by the hormone,J Na + increased from 107±33 to 148±30 andJ Cl − from 121±33 to 165±32 pmol·min−1 mm−1. The rise inJ NaCl was accompanied by an increase in PDte from 9.0±0.7 to 13.5±0.9 mV and a decrease in Rte from 14.4±2.0 to 11.2±1.7 Ω cm2. No K+ net transport was detected, either under control conditions or in the presence of AVP. To test for a possible effect of HCO 3 − on transepithelial ion fluxes, mTAL segments were bathed and perfused with HCO 3 − containing Ringer solutions. With the exception ofJ Ca 2+ which was significantly different from zero (J Ca 2+: 0.26±0.06 pmol·min−1 mm−1), net transepithelial fluxes of Na+, Cl−, K+ and Mg2+ were unaffected by HCO 3 − . In the presence of AVP,J Mg 2+ andJ Ca 2+ were unaltered whereasJ NaCl was stimulated to the same extent as observed in the absence of HCO 3 − . In conclusion our results indicate heterogeneity of response to AVP in cortical and medullary segments of the TAL segment, since AVP stimulates Ca2+ and Mg2+ reabsorption in the cortical part and Na+ and Cl− reabsorption in the medullary part of this nephron segment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582541
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  • 3
    Electronic Resource
    Electronic Resource
    A voltage-dependent ionic channel in the basolateral membrane of late proximal tubules of the rabbit kidney (1986)
    Springer
    Pflügers Archiv 407 (1986), S. S142 
    Details
    ISSN: 1432-2013
    Keywords: Late proximal tubule (pars recta) ; Patch-clamp ; Basolateral membrane ; Ionic channel ; Diphenylamine-2-carboxylate ; SITS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The patch-clamp method was applied to the lateral membrane of late proximal tubules of the rabbit kidney. Tubule segments were cannulated on one side by a perfusion system. At the noncannulated end of the tubules, the lateral membrane was accessible to a patch pipette. In cell-attached, as well as cell-excised (presumably inside-out oriented) membrane patches, a voltage sensitive channel was observed. The open-state probability of this channel increased with depolarizing potentials. In cell-excised patches bathed with NaCl-Ringer on both sides, the single channel conductance g was 28.0±1.2 pS (n=10). With KCl-Ringer in the pipette and NaCl-Ringer in the bath g was 24.7±1.3 pS (n=7) and the current-voltage curve crossed the axis at 0 mV. Therefore, the channel does not discriminate between K+ and Na+ ions. Replacing half of NaCl by mannitol on the bath side yielded a permeability for cations about twice as high as for Cl−. The channel could be reversibly blocked by diphenylamine-2-carboxylate (DPC), whereas its inhibition by SITS was only partially reversible. In cell-attached patches, the channel was nearly inactivated at zero clamp potential, but became active when the membrane patch was depolarized. The significance of this nonselective channel for proximal tubule cell function is still unclear. It could be involved in the contraluminal exit mechanism of various anions. However, it could also play a role in cell volume regulation processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584943
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  • 4
    Electronic Resource
    Electronic Resource
    Cl−-channel blockers in the thick ascending limb of the loop of Henle Structure activity relationship (1986)
    Springer
    Pflügers Archiv 407 (1986), S. S128 
    Details
    ISSN: 1432-2013
    Keywords: Cl−-channel blocker ; Thick ascending limb of the loop of Henle ; Diphenylamine-2-carboxylate ; Cl−-channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract On the basis of our findings with diphenylamine-2-carboxylate [5] we have searched for compounds which possess an even higher affinity for the Cl−-channels in the basolateral membrane of the thick ascending limb of the loop of Henle. To quantitiy the inhibitory potency, we performed measurements of the equivalent short circuit current, corresponding to the secondary active transport of Cl− [8] and measurements of the voltage across the basolateral membrane. A survey of 219 compounds reveals that relatively simple modifications in the structure of diphenylamine-2-carboxylate led to very potent blockers such as 5-nitro-2-(3-phenylpropylamino)-benzoate which inhibits the short circuit current half maximally (IC50) at 8·10−8 mol/l. A comparison of the structural formula and the respective IC50 values leads to several empirical conclusions: 1. The potent compounds are lipophilic due to the apolar residue (e.g. phenyl- or cycloalkyl group). Replacing this part of the molecule by an aliphatic chain (up to 4 C-atoms) leads to inactive compounds. 2. Most of the inhibitors are secondary amines. Linking other than with-NH- between the phenyl ring and the benzoic acid results in inactive compounds. Tertiary amines, such as in case of 2-(N,N-diphenylamine) benzoic acid or N-methylphenylaminebenzoic acid are poorly active. 3. The carboxylate group of the benzoate moiety must be in ortho position to the amino group. 4. Introduction of substituents into the benzoate moiety e.g.-NO2 (in meta position to the carboxylate group), or by-Cl (in para position to the carboxylate group) results in an increase of inhibitory potency. 5. A-CH2-,-C2H4-,-C3H6-) spacer between the amino bridge and the phenyl ring increases the affinity for the Cl−-channel by several orders of magnitude. The above described structure activity relationship renders it likely that these chloride channel blockers possess several sites of interaction: The negatively charged carboxylate group, the secondary amine group which probably carries a positive partial charge, and for the very potent agents (nos. 130, 143, 144, and 145) an additional negative partial charge at the respective-Cl or-NO2 substituent. Finally, also an apolar interaction with an cycloalkyl or cycloaryl residue seems to be required, and this site of interaction has a defined spacing from the secondary amino nitrogen.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584942
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  • 5
    Electronic Resource
    Electronic Resource
    Torasemide inhibits NaCl reabsorption in the thick ascending limb of the loop of Henle (1986)
    Springer
    Pflügers Archiv 407 (1986), S. 611-614 
    Details
    ISSN: 1432-2013
    Keywords: Torasemide ; Na+2Cl−K+ carrier ; Cl−-channel ; Thick ascending limb of the loop of Henle ; Mouse ; Rabbit
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Torasemide (1-isopropyl-(4-(3-methylphenylamino)pyrid-3-yl)urea) is a new diuretic. The present study examines the effects of this substance in the isolated perfused thick ascending limb (TAL) of mouse and rabbit kidney. In cortical TAL segments of the rabbit, torasemide added to the lumen perfusate led to a fall in equivalent short circuit current (= transepithelial voltage divided by transepithelial resistance, which corresponds to the rate of chloride reabsorption) with a half maximal inhibition concentration of 3 · 10−7 mol/l. This effect was accompanied by a hyperpolarization of the luminal and basolateral membrane from −78 to −81 mV and from −72 to −81 mV, respectively. A similar hyperpolarization of both membrane voltages was also observed in medullary TAL segments of the mouse. Torasemide, added to the basolateral perfusate of cortical TAL segments of the rabbit, also inhibited the equivalent short circuit current. However, 3 · 10−5 mol/l were necessary for a half maximal inhibition. The fall in the equivalent short circuit current was accompanied by a significant increase in transepithelial resistance from 34 to 38 Ω cm2, by an increase in the fractional resistance of the basolateral membrane, and by a hyperpolarization mainly of the basolateral membrane. Again, similar results were obtained in the medullary TAL segment of the mouse. The strong inhibitory effect of torasemide from the lumen side can be explained by an interference with the Na+ 2Cl−K+ carrier in the luminal membrane. In fact, torasemide apparently is structurally related to furosemide. The weaker effect of torasemide from the peritubular side can, at least in part, be explained as an interference with chloride channels present in the basolateral membrane. Torasemide is also structurally related to chloride channel blockers such as diphenylamine-2-carboxylate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582640
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  • 6
    Electronic Resource
    Electronic Resource
    Effects of glucagon on Na+, Cl−, K+, Mg2+ and Ca2+ transports in cortical and medullary thick ascending limbs of mouse kidney (1989)
    Springer
    Pflügers Archiv 414 (1989), S. 640-646 
    Details
    ISSN: 1432-2013
    Keywords: Glucagon ; Transepithelial ion net fluxes ; Na+, Cl−, K+, Ca2+, Mg2+ transport ; Electron microprobe ; Mouse kidney ; In vitro microperfusion ; Cortical and medullary thick ascending limb of Henle's loop ; In vivo micropuncture study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The effects of glucagon on transepithelial Na+, Cl−, K+, Ca2+ and Mg2+ net fluxes were investigated in isolated perfused cortical (cTAL) and medullary (mTAL) thick ascending limbs of Henle's loop of the mouse nephron. Transepithelial ion net fluxes (J Na +,J Cl −,J K +,J Ca 2+,J Mg 2+) were determined by electron probe analysis of the collected tubular fluid. Simultaneously the transepithelial voltage (PDte) and the transepithelial resistance (R te) were recorded. In cTAL-segments (n=8), glucagon (1.2×10−8 mol · l−1) stimulated significantly the reabsorption of Na+, Cl−, Ca2+ and Mg2+∶J Na + increased from 204±20 to 228±23 pmol · min−1 · mm−1,J Cl − from 203±18 to 234±21 pmol · min−1 · mm−1,J Ca 2+ from 0.52±0.13 to 1.34±0.30 pmol · min−1 · mm−1 andJ Mg 2+ from 0.51±0.08 to 0.84±0.08 pmol · min−1 · mm−1.J K+ remained unchanged: 3.2±1.3 versus 4.0±1.9 pmol · min−1 · mm−1. Neither PDte (16.3±1.5 versus 15.9±1.4 mV) norR te (22.5±3.0 versus 20.3±2.6 Ωcm2) were changed significantly by glucagon. However, in the post-experimental periods a significant decrease in PDte and increase inR te were noted. In mTAL-segments (n=9), Mg2+ and Ca2+ transports were close to zero and glucagon elicited no significant effect. The reabsorptions of Na+ and Cl−, however, were strongly stimulated:J Na + increased from 153±17 to 226±30 pmol · min−1 · mm−1 andJ Cl − from 151±23 to 243±30 pmol · min−1 · mm−1. The rise in NaCl transport was accompanied by an increase in PDte from 10.3±1.1 to 12.3±1.2 mV and a decrease inR te from 19.1±2.7 to 17.8±2.0 Ωcm2. No net K+ movement was detectable either in the absence or in the presence of glucagon. A micropuncture study carried out in hormone-deprived rats indicated that glucagon stimulates Na+, Cl−, K+, Mg2+ and Ca2+ reabsorptions in the loop of Henle. In conclusion our data demonstrate that glucagon stimulates NaCl reabsorption in the mTAL segment and to a lesser extent in the cTAL segment whereas it stimulates Ca2+ and Mg2+ reabsorptions only in the cortical part of the thick ascending limb of the mouse nephron. These data are in good agreement with, and extend, those obtained in vivo on the rat with the hormone-deprived model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582129
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