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  • Electronic Resource  (32)
  • Exocrine secretion  (14)
  • Cl− conductance  (11)
  • Micropuncture  (7)
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  • Electronic Resource  (32)
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  • 1
    Electronic Resource
    Electronic Resource
    Evidence for a bicarbonate leak in the proximal tubule of the rat kidney (1980)
    Springer
    Pflügers Archiv 386 (1980), S. 239-244 
    Details
    ISSN: 1432-2013
    Keywords: Bicarbonate transport ; Proximal tubule ; Rat kidney ; Antimony microelectrode ; Micro-Astrup ; Benzolamide ; Micropuncture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To elucidate the mechanism responsible for the establishment of steady state pH at zero net flux (pH∞) in proximal convoluted tubules, luminal pH was recorded continuously with antimony microelectrodes under three experimental conditions. First: luminal pH in stationary droplets was allowed to reach pH∞ (6.76±0.07) and then carbonic anhydrase inhibitor benzolamide (3·10−3 mol/l) was superfused on the kidney surface. Following application of benzolamide, luminal pH decreased within seconds (ΔpH=−0.27±0.03 SEM). Second: tubule segments were perfused continuously with MES-buffer containing solution set to a pH of 6.1. Some 1–2 mm distal to the perfusion pipette luminal pH was recorded and was 6.5±0.04. After superfusion of benzolamide (3·10−3 mol/l) pH decreased (ΔpH=−0.15±0.03). Third: pH in stationary droplets was again allowed to reach pH∞ (6.69±0.01) and bicarbonate and CO2-free solution (5 mmol/l phosphate set to a pH of 7.4) was microinfused into the adjacent peritubular capillary. Luminal pH again decreased almost immediately (ΔpH=−0.23±0.02). The data are interpreted as evidence for a bicarbonate leak. In a fourth series of experiments, segments of proximal tubules were perfused under benzolamide (0.4·10−6 mol/min) with solutions initially free of bicarbonate or other buffers. In the collected fluid, bicarbonate was determined by a micro-Astrup method. A significant increase of luminal bicarbonate concentration (r=0.88) indicates a permeability of 0.98±0.14·10−6 cm2/s of the tubular wall for bicarbonate. Since bicarbonate eventually increases more than 3-fold the equilibrium concentration, collected bicarbonate could not have been formed by H2CO3 or CO2. Bicarbonate enters the luminal fluid and reacts with secreted hydrogen ions to form carbonic acid. It, therefore, buffers secreted hydrogen ions and increases luminal pH at or below steady state. Inhibition of carbonic anhydrase and lowering of peritubular bicarbonate thus lower pH∞.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587474
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of human sweat duct chloride conductance by chloride channel blockers (1987)
    Springer
    Pflügers Archiv 408 (1987), S. 511-514 
    Details
    ISSN: 1432-2013
    Keywords: Human sweat duct ; Cl− conductance ; Cl− channel blockers ; Cystic fibrosis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract To characterize the chloride conductance of human sweat duct the effect of various analogues of diphenylamine-2-carboxylate was investigated on the transepithelial potential difference (PDT) and resistance (R T ) of isolated microperfused sweat ducts. Although the most powerful analogues which block Cl− channels in various secretory and absorptive epithelia were ineffective, a number of analogues (in particular Cl substituted ones) were found which at high concentrations significantly and reversibly increased PDT andR T . The data suggest that the main chloride conductance pathway of sweat duct epithelium resides in the cell membranes rather than in the tight junctions. In addition the different blocking spectra of the chloride conductances of sweat duct and tracheal epithelium (Welsh MJ, Science 232:1648, 1986) suggest that the combined impairment of both conductances in cystic fibrosis does not result from a molecular defect in the Cl− channels.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585077
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  • 3
    Electronic Resource
    Electronic Resource
    Carbonic anhydrase independent bicarbonate reabsorption (1982)
    Springer
    Pflügers Archiv 395 (1982), S. 121-125 
    Details
    ISSN: 1432-2013
    Keywords: Bicarbonate ; Renal tubular transport ; Carbonic anhydrase inhibition ; Permeability ; Microperfusion ; Micropuncture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The present study was designed to define the prerequisites of carbonic anhydrase independent bicarbonate reabsorption. In free flow experiments during systemic application of carbonic anhydrase inhibitor benzolamide (50 mg/kg B. W.) bicarbonate recovery in % of filtered load was found to be 74±8% in late proximal convoluted tubules, 39±6% in distal convoluted tubules and 32±4% in urine, indicating that most of carbonic anhydrase independent bicarbonate reabsorption occurs in tubule segments prior to distal convoluted tubules. In vivo continuous microperfusion experiments in proximal convoluted tubules demonstrated that luminal benzolamide (0.5 mmol/l) virtually abolishes net bicarbonate fluxes, when bicarbonate concentration in the luminal perfusate (25 mmol/l) is close to peritubular plasma concentration (24.4 mmol/l). In contrast, a significant downhill reabsorptive flux occurs, when perfusate bicarbonate concentration is 75 mmol/l and a significant downhill secretory flux is observed, when the perfusate is initially free of bicarbonate. The corresponding apparent permeabilities are 1.0±0.1·10−6 cm2/s for influx and 1.6±0.4·10−6 cm2/s for efflux of bicarbonate. Clearance studies reveal that carbonic anhydrase dependent and independent bicarbonate reabsorption are not saturable but depend on the rate of volume reabsorption in the kidney. In conclusion, passive movements of bicarbonate do occur in proximal convoluted tubules and most likely contribute to carbonic anhydrase independent bicarbonate reabsorption.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584724
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  • 4
    Electronic Resource
    Electronic Resource
    Handling of allantoin by the rat kidney (1975)
    Springer
    Pflügers Archiv 357 (1975), S. 201-207 
    Details
    ISSN: 1432-2013
    Keywords: Allantoin ; Uricase ; Kidney ; Clearance ; Micropuncture ; Rat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Renal excretion of allantoin was measured by tracer techniques. After injection of 2-C14 urate and H3 inulin, clearances of allantoin and inulin were measured and both proximal and distal tubules were micropunctured. In confirmation of earlier results 2-C14 urate injected into an intact animal is very rapidly converted to C14 allantoin: after 15 min more than 90% of urinary tracer is present as allantoin. It was further observed that 1) allantoin clearance is essentially identical with inulin clearance over a wide range of urine flows; 2) no net transport of allantoin occurs in either proximal or distal tubules. Clearly allantoin is handled by the rat kidney like inulin. The total excretion of filtered allantoin unlike that of filtered urate provides an easy and effective mechanism for animals possessing the enzyme uricase to dispose of their purine loads.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585975
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of benzolamide on luminal pH in proximal convoluted tubules of the rat kidney (1978)
    Springer
    Pflügers Archiv 375 (1978), S. 39-43 
    Details
    ISSN: 1432-2013
    Keywords: Proximal tubule ; Micropuncture ; Carbonic anhydrase ; Benzolamide ; Acidification
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Luminal pH in early and late proximal tubules was recorded continuously with antimony microelectrodes before and during carbonic anhydrase inhibition. Following i.v. application of benzolamide (25 μmol/kg BW), luminal pH decreased almost immediately in early proximal tubules (ΔpH −0.42±0.06 SEM), but increased in late proximal tubules (ΔpH +0.27±0.06). Urinary pH increased (ΔpH +1.6±0.16) after a delay of some 30 s. Similar results, i.e. decrease of pH in early and increase of pH in late proximal tubules, were obtained, when benzolamide containing solutions were microinfused into early proximal tubules or superfused on the nephron surface. In contrast, luminal pH decreased in late proximal tubules, when benzolamide was microinfused into the same nephron segment. The decrease of luminal pH indicates inhibition of luminally active carbonic anhydrase, leading to delayed buffering of secreted hydrogen ions. The increase of luminal pH in late proximal tubules may be attributed to several factors including increased delivery of bicarbonate, impaired bicarbonate exit at the antiluminal membrane and decreased hydrogen ion formation in the tubular cell due to inhibition of cellular carbonic anhydrase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00584146
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  • 6
    Electronic Resource
    Electronic Resource
    Properties of the luminal membrane of isolated perfused rat pancreatic ducts (1988)
    Springer
    Pflügers Archiv 411 (1988), S. 546-553 
    Details
    ISSN: 1432-2013
    Keywords: Pancreas ; Isolated perfused ducts ; Luminal membrane ; Cl− conductance ; Cl−/HCO 3 − antiport ; cAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The aim of the present study was to investigate by what transport mechanism does HCO 3 − cross the luminal membrane of pancreatic duct cells, and how do the cells respond to stimulation with dibytyryl cyclic AMP (db-cAMP). For this purpose a newly developed preparation of isolated and perfused intra-and interlobular ducts of rat pancreas was used. Responses of the epithelium to inhibitors and agonists were monitored by electrophysiological techniques. Addition of HCO 3 − /CO2 to the bath side of nonstimulated ducts depolarized the PD across the basolateral membrane (PDbl) by about 9mV, as also observed in a previous study [21]. This HCO 3 − effect was abolished by Cl− channel blockers or SITS infused into the lumen of the duct: i. e. 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB, 10−5 M) hyperpolarized PDbl by 8.2±1.6 mV (n=13); 3′,5-dichlorodiphenylamine-2-carboxylic acid (DCl-DPC, 10−5 M) hyperpolarized PDbl by 10.3±1.7 mV (n=10); and SITS hyperpolarized PDbl by 7.8±0.9 mV (n=4). Stimulation of the ducts with dbcAMP in the presence of bath HCO 3 − /CO2 resulted in depolarization of PDbl, the ductal lumen became more negative and the fractional resistance of the luminal membrane decreased. Together with forskolin (10−6 M), db-cAMP (10−4 M) caused a fast depolarization of PDbl by 33.8±2.5 mV (n=6). When db-cAMP (5×10−4 M) was given alone in the presence of bath HCO 3 − /CO2, PDbl depolarized by 25.3±4.2 mV (n=10). In the absence of exogenous HCO 3 − , db-cAMP also depolarized PDbl by 24.7±3.0 mV (n=10). The present data suggest that in the luminal membrane of pancreatic duct cells there is a Cl− conductance in parallel with a Cl−/HCO 3 − antiport. Dibutyryl cyclic AMP increases the Cl− conductance of the luminal membrane. Taking together our present results, and the recent data obtained for the basolateral membrane [21], a tentative model for pancreatic HCO 3 − transport is proposed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582376
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  • 7
    Electronic Resource
    Electronic Resource
    Handling of uric acid by the rat kidney (1971)
    Springer
    Pflügers Archiv 324 (1971), S. 279-287 
    Details
    ISSN: 1432-2013
    Keywords: Uric Acid Secretion ; Micropuncture ; Renal Tubule ; Ultramicro Analysis ; Harnsäuresekretion ; Mikropunktion ; Nierentubulus ; Ultramikroanalyse
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Mit Hilfe der Mikropunktionstechnik und einer neu entwickelten Methode der Ultramikroanalyse wurde der Harnsäuretransport am proximalen Tubulus der Rattenniere untersucht. Unter normalen Bedingungen ohne Harnsäureinfusion und ohne osmotische Diurese konnte eine Harnsäure-Netto-Sekretion im proximalen Tubulus nachgewiesen werden. Dabei war in diesen Experimenten die Inulinclearance etwa doppelt so groß wie die Harnsäureclearance. In der Bilanz wurde also mehr Harnsäure resorbiert als sezerniert, aber nicht, wie früher angenommen, im proximalen Tubulus.
    Notes: Summary Uric acid transport in the rat proximal tubule was studied by micropuncture and a new method of chemical ultramicro analysis. Under normal free-flow conditions at physiological levels of uric acid plasma concentrations a net secretion of uric acid in the proximal tubule was demonstrated. In these experiments the clearance ratio of uric acid to inulin was in the range of 0.4 which is normal in antidiuretic rats. Net reabsorption of uric acid, therefore, took place in the kidney, but certainly not in the proximal tubule as previously suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00592456
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  • 8
    Electronic Resource
    Electronic Resource
    Chloride channels in the luminal membrane of rat pancreatic acini (1997)
    Springer
    Pflügers Archiv 434 (1997), S. 188-194 
    Details
    ISSN: 1432-2013
    Keywords: Key words Exocrine pancreas ; Cl ; channel ; Cl ; secretion ; Exocrine secretion ; Patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Pancreatic acini secrete Na+, Cl–and H2O in response to secretagogues such as acetylcholine. Cl–channels in the luminal membrane are a prerequisite for this secretion. The properties of the corresponding conductance have previously been examined using whole-cell recordings. The present study attempts to examine the properties of the single channels in cell-attached and cell-free excised patches from the luminal membrane. To this end the pipettes were filled with an N-methyl-D-glucamine (NMDG+) chloride/gluconate solution. The voltage-clamp range was chosen to be pipette positive (cell negative, –60 to –130 mV) in order to increase the driving force for outward Cl–currents. Under resting conditions cell attached luminal patches had very few single-channel currents (12 out of 45 experiments). Their incidence was sharply increased by carbachol (CCH, 1 μmol/l) in 41 out of 45 experiments. The single-channel conductance of these channels was 1.97 ± 0.05 pS. The properties of these channels in excised patches were examined further: their single-channel conductance was 2.2 ± 0.07 pS (n = 59) and their conductance selectivity was I– 〉 Br– 〉 Cl– 〉〉 gluconate. None of the typical Cl–channel blockers (DIDS, NPPB, glibenclamide 100 μmol/l) blocked these channels. It is concluded that the luminal membrane of the rat pancreatic acinus possesses Cl–channels with very low conductance which are activated by carbachol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050382
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  • 9
    Electronic Resource
    Electronic Resource
    Transmitter-induced changes of the membrane voltage of HT29 cells (1992)
    Springer
    Pflügers Archiv 421 (1992), S. 224-229 
    Details
    ISSN: 1432-2013
    Keywords: Cl− conductance ; HT29 ; P2 receptor ; Colon ; Cl− secretion ; cAMP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The colonic carcinoma cell line HT29 was used to examine the influence of agonists increasing cytosolic cAMP and Ca2+ activity on the conductances and the cell membrane voltage (V m). HT29 cells were grown on glass cover-slips. Cells were impaled by microelectrodes 4–10 days after seeding, when they had formed large plaques. In 181 impalements V m was −51±1 mV. An increase in bath K+ concentration from 3.6 mmol/l to 18.6 mmol/l or 0.5 mmol/l Ba2+ depolarized the cells by 10±1 mV (n=49) or by 9±2 mV (n=3), respectively. A decrease of bath Cl− concentration from 145 to 30 mmol/l depolarized the cells by 11±1 mV (n=24). Agents increasing intracellular cAMP such as isobutylmethylxanthine (0.1 mmol/l), forskolin (10 μmol/l) or isoprenaline (10 μmol/l) depolarized the cells by 6±1 (n=13), 15±3 (n=5) and 6±2 (n=3) mV, respectively. In hypoosmolar solutions (225 mosmol/l) cells depolarized by 9±1 mV (n=6). Purine and pyrimidine nucleotides depolarized the cells dose-dependently with the following potency sequence: UTP 〉 ATP 〉 ITP 〉 GTP 〉 TIP 〉 CTP = 0. The depolarization by ATP was stronger than that by ADP and adenosine. The muscarinic agonist carbachol led to a sustained depolarization by 27±6 mV (n=5) at 0.1 mmol/l, and to a transient depolarization by 12±4 mV (n=5) at 10 μmol/l. Neurotensin depolarized with a half-maximal effect at around 5 nmol/l. The depolarization induced by nucleotides and neurotensin was transient and followed by a hyperpolarization. We confirm that HT29 cells possess Cl−- and K+-conductive pathways. The Cl− conductance is regulated by intracellular cAMP level, cytosolic Ca2+ activity, and cell swelling. The K+ conductance in HT29 cells is regulated by intracellular Ca2+ activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00374831
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  • 10
    Electronic Resource
    Electronic Resource
    Regulation of the Na+2Cl–K+ cotransporter in in vitro perfused rectal gland tubules of Squalus acanthias (1998)
    Springer
    Pflügers Archiv 436 (1998), S. 521-528 
    Details
    ISSN: 1432-2013
    Keywords: Key words cAMP ; Cl ; channels ; Cl ; secretion ; Exocrine secretion ; K+ channels ; Volume regulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Previously it has been shown that the Na+2Cl–K+ cotransporter accepts NH4 + at its K+ binding site. This property can be used to estimate its transport rates by adding NH4 + to the bath and measuring the initial furosemide-dependent rates of change in BCECF fluorescence. We have utilized this technique to determine the regulation of the furosemide-inhibitable Na+2Cl–K+ cotransporter in in vitroperfused rectal gland tubules (RGT) of Squalus acanthias. Addition of NH4 + to the bath (20 mmol/l) led to an initial alkalinization, corresponding to NH3 uptake. This was followed by an acidification, corresponding to NH4 + uptake. The rate of this uptake was quantified by exponential curve fitting and is given in arbitrary units (Δfluorescence/time). This acidification could be completely inhibited by furosemide. In the absence of any secretagogue preincubation of RGT in a low Cl– solution (6 mmol/l, low Cl–) for 10 min enhanced the uptake rate significantly from 4.04±0.51 to 12.7±1.30 (n=5). The addition of urea (200 mmol/l) was without effect, but the addition of 300 mmol/l mannitol (+300 mannitol) enhanced the rate significantly from 7.24±1.33 to 14.7±4.6 (n=6). Stimulation of NaCl secretion by a solution maximizing the cytosolic cAMP concentration (Stim) led to a significant increase in NH4 + uptake rate from 5.00±1.33 to 13.3±1.54 (n=6). Similar results were obtained in the additional presence of Ba2+ (1 mmol/l): the uptake rate was increased significantly from 4.23±0.34 to 15.1±1.86 (n=16). In the presence of Stim low Cl– had no additional effect on the uptake rate: 15.1±3.1 versus 15.2±2.8 in high Cl– (n=6). The uptake rate in Stim containing additional +300 mannitol (22.3±4.0, n=5) was not significantly different from that obtained with Stim or +300 mannitol alone. By whatever mechanism the NH4 + uptake rate was increased furosemide (500 µmol/l) always reduced this rate to control values. Hence three manoeuvres enhanced furosemide-inhibitable uptake rates of the Na+2Cl–K+ cotransporter probably independently: (1) lowering of cytosolic Cl– concentration; (2) cell shrinkage; and (3) activation by cAMP.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050667
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