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  • 1
    Electronic Resource
    Electronic Resource
    Osmotic water permeability of the apical membrane of proximal straight tubular (PST) cells (1984)
    Springer
    Pflügers Archiv 402 (1984), S. 337-339 
    Details
    ISSN: 1432-2013
    Keywords: Osmotic water permeability ; leaky epithelia ; kidney tubule ; cell water permeability ; apical permeability ; water transport ; ion transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Osmotic steps, ΔC, were produced across the apical cell membrane of isolated rabbit PST by perfusing their lumens with double barreled micropipettes at a rate of 0.5–0.8 nl/s. ΔC=15–46 mOsmolar were induced with mannitol. Changes in luminal diameter were recorded as a function of time with a TV camera and an integrator-processor system with space and time resolutions of 0.03 μm and 0.0167 s (3). The tubules were bathed with oil. Outer tubule diameter was time invariant. P os ca , the apical cell osmotic permeability was therefore calculated from cell volume changes with time in units of 10−4 cm3/cm2. s. Osmolar. P os ca was independent of ΔC. The mean is 22.8±1.3 (n=55). With a basolateral permeability of 50.4 (3,12), the transcellular permeability is 14 (same units) smaller than the transepithelial values available. This leads to the conclusion that a significant paracellular water osmotic permeability must exist.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00585520
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  • 2
    Electronic Resource
    Electronic Resource
    Solvent drag of sucrose during absorption indicates paracellular water flow in the rat kidney proximal tubule (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 541-547 
    Details
    ISSN: 1432-2013
    Keywords: Water absorption ; Paracellular flow ; Solvent drag ; Rat proximal tubule ; Leaky epithelia ; Kidney tubule ; Epitnelial transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Single convoluted proximal tubules of the rat kidney were lumen perfused in situ with isosmotic solutions containing C14-sucrose and H3-inulin as tracers, to evaluate whether the extracellular marker sucrose is entrained by water during proximal tubular reabsorption. Inulin was used as volume marker. The absorptive rate was varied by using as luminal perfusion fluids either a solution made up of (in mmole/l) 120 NaCl, 5 glucose, 25 NaHCO3 and altering the perfusion rate, or a solution containing 110 NaCl and 70 raffinose.J S, the net sucrose efflux is found to be a function of the net volume flow,J V, such that atJ V=0,J S is very small and at high rates ofJ V,J S is over 60-fold the value observed at lowJ V values. In addition, the transported to luminal sucrose concentrations decreased withJ V in a hyperbolic manner. Unstirred layers affect the diffusive component ofJ S, but only to a small extent. Therefore, the large remaining dependency ofJ S withJ V must be due to drag of sucrose by water, within the paracellular pathway. This leads to the conclusion that water flows through the paracellular pathway during absorption in the rat proximal tubule, in addition to transcellular water flow. Using equations for molecular sieving and the measured value of σs for sucrose of 0.76–0.91, it is calculated that the pathway where entrainment of solute by water occurs must be 1.0–1.1 nm wide. This calculation is only tentative since σs depends on the as yet unknown relative contribution of transcellular and paracellular pathways to transepithelial water osmotic permeability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00582545
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  • 3
    Electronic Resource
    Electronic Resource
    Abnormal transtubular permeability to raffinose during intravenous infusion of urea and of mannitol in the intact dog kidney (1980)
    Springer
    Pflügers Archiv 383 (1980), S. 165-171 
    Details
    ISSN: 1432-2013
    Keywords: Paracellular pathway ; Nephron permeability ; Urea diuresis ; Osmotic diuresis ; Dog kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Serial urine samples were collected every 3 s after a bolus injection containing labelled raffinose plus a “glomerular substance” (i.e. a substance eliminated only by filtration like inulin or dextran MW 15,000–17,000) into the renal artery of dogs. Three groups of dogs were explored. They underwent profuse diuresis subsequent to i.v. infusion of saline alone (S), saline + urea (U) or saline + mannitol (M) respectively. The amount of raffinose and of “glomerular substances” eliminated in the urine was plotted as a function of a normalizedurine volume. Aurine volume of 100% is defined as the urinary volume collected from the time of injection up to the moment in which urinary concentration of the glomerular substance reaches 50% of its peak concentration. In the three groups, elimination of “glomerular substances” began 50–60 s after the bolus injection corresponding to aurine volume of 65.9±0.9%. In the S group raffinose was eliminated after aurine volume of 54.7%. A fraction equal to (3.5±1.0)×10−4 of the amount of raffinose injected in the bolus preceeded elimination of “glomerular substances”. In the U group, a fraction equal to (21.9±5.3)×10−4 of the amount of raffinose injected preceeded climination of “glomerular substances”. This value is statistically higher than that obtained in the S group. In the U group, raffinose was eliminated 15–20 s after injection, corresponding to aurine volume of 18.8%. This urine volume is not different from that occupied by catheter, ureter and renal pelvis. It is concluded that raffinose, is eliminated ahead of dextran in the U group because a small but significant amount of raffinose crosses the tubular wall. Thus, urea infusion opens the paracellular pathways since raffinose stays in the extracellular space. Animals of the M group also showed an early appearance of raffinose although at a less distal level of the nephron.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581878
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  • 4
    Electronic Resource
    Electronic Resource
    Effect of hypertonic urea and mannitol on distal nephron permeability (1977)
    Springer
    Pflügers Archiv 368 (1977), S. 3-11 
    Details
    ISSN: 1432-2013
    Keywords: Distal nephron permeability ; Luminal hypertonicity ; Urea permeability ; Mannitol permeability ; Paracellular pathway ; Saline diuresis ; Urea diuresis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The paracellular pathway permeability is known to increase in perfused amphibian kidneys if the luminal fluid is made hyperosmotic with mannitol or urea. To investigate whether luminal hypertonicity increases paracellular pathway permeability in the mammalian nephron, early rat distal tubules were micropunctured and perfused through one micropipette with either isosmotic saline (IS), hyperosmotic urea (HU) or hyperosmotic mannitol (HM) solutions. A second micropipette was placed down-stream in the same tubule and test solutions of 30 nl of a mixture of14C-inulin and3H-mannitol or of3H-inulin and14C-urea were injected. Similar intratubular injections of tracers were performed in a second group of rats undergoing diuresis induced either by infusing intravenously saline alone (VS) or receiving saline plus 0.4 M urea (VU). In the latter group (VU) luminal urea concentration was increased without the tubular lumen being made hyperosmotic to its peritubular fluid. Urinary inulin recovery was essentially complete and unaffected by experimental procedures. Difference between mannitol recoveries in isosmotic saline and hyperosmotic urea perfusions IS-HU was 2.6±0.8% (P〈0.001). Difference in urea recoveries IS-HM was 4.1±5.1% (P〉0.40), IS-HU was 13.9±5.3% (P=0.015) and, VS-VU=17.0±3.4 (P〈0.001). Therefore, elevated luminal urea concentration increased tracer mannitol and also tracer urea permeability, both in the presence and absence of tubular hyperosmolarity. Electron microscopic observations showed changes in geometry of tubular junctional complexes compatible with the observed increase in permeability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01063448
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  • 5
    Electronic Resource
    Electronic Resource
    The continuous measurement of tubular volume changes in response to step changes in contraluminal osmolality (1984)
    Springer
    Pflügers Archiv 400 (1984), S. 343-348 
    Details
    ISSN: 1432-2013
    Keywords: Tubular permeability ; Epithelial water transport ; Volume changes ; Kidney proximal tubule ; Water osmotic permeability ; Proximal water transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A new method to measure time dependent (t) volume (V) changes in proximal straight tubules (PST) is described.V is calculated from diameter (d) measurements for which a video camera and an integrating circuit are used. A tubular image of high optical contrast is recorded with the TV camera such that the scan lines run crosswise to the tubule. The video signal is analyzed by a special processor which adds 225 tubular diameters of each TV frame and feeds this analog signal to a pen recorder. The fractional error ind measurements is 10−3. Diameter changes of less than 0.05 μm can be detected, as compared to the usual error of a single measurement of about 0.4 μm.P os cb , the osmotic water permeability of the contraluminal cell membrane was measured by setting up osmotic steps across it in less than 0.1 s and following the ensuing Δd/Δt. the time delay between solution change and the linear part of the osmotic response was 0.51±0.05 s.P os cb was found to be 50.4 (±8.7)×10−4 cm3·cm−2 of basement membrane area ·s−1·osmolar−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587530
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  • 6
    Electronic Resource
    Electronic Resource
    Widening of the paracellular pathway in the kidney tubule by a transtubular osmotic gradient (1974)
    Springer
    Pflügers Archiv 351 (1974), S. 1-12 
    Details
    ISSN: 1432-2013
    Keywords: Paracellular Shunt Pathway ; Transtubular Permeability ; Perfused Toad Kidney ; Transtubular Osmotic Gradient ; Kidney ; Epithelia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Trace amounts of either labelled mannitol, sucrose, raffinose or inulin were added to the portal circulation in the doubly perfused toad kidney and their-urine-to-portal fluid, labelled molecules-to-chemical inulin ratio (denoted here asR) was evaluated. Under control isosmotic conditionsR was found to be inversely related to the probing molecule radius.R for inulin was practically zero.R for all probing molecules rose reversibly when the luminal fluid was rendered hyperosmotic by addition of 50 mmole mannitol to the aortic circulation, and even more so when 50 mmole urea was added per liter of aortic fluid. ThusR for raffinose rose from 0.0025±0.0002 (control) to 0.0126±0.0012 (+50 mM mannitol) and to 0.0967±0.0112 (+50 mM urea). This increase inR must be due to widening of the paracellular shunt pathway since the contribution of portal circulation to the glomerular filtrate was negligible and these molecules are known to stay extracellular. The present experiments suggest that transtubular urea (and osmotic) gradients may play a role in the regulation of the size of the paracellular shunt pathway.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00603506
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  • 7
    Electronic Resource
    Electronic Resource
    A standard nomenclature for structures of the kidney (1988)
    Springer
    Pflügers Archiv 411 (1988), S. 113-120 
    Details
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00581654
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  • 8
    Electronic Resource
    Electronic Resource
    Comparison of transcellular and transepithelial water osmotic permeabilities (P os) in the isolated proximal straight tubule (PST) of the rabbit kidney (1988)
    Springer
    Pflügers Archiv 412 (1988), S. 66-74 
    Details
    ISSN: 1432-2013
    Keywords: Osmotic permeability ; Paracellular water flow ; Proximal tubule ; PST ; Transcellular permeability ; Epithelia ; Water transport ; Leaky epithelia ; Kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Measurements of the water osmotic permeabilities of apical and basolateral membranes of PST cells and of the transepithelial permeability have been carried out using a very fast method with high temporal and spatial resolution. At 25°C the values obtained are: 80.8±11.9×10−4 cm3/s osmol cm2 of apical (luminal) surface area and 90.1 ±13.0×10−4 cm3/s osmol cm2 of basement membrane area (no membrane invaginations taken in account). These values are higher than previously published values due to the use of a faster and more accurate volume measuring and recording system. The transepithelial water osmotic permeability at 25°C is 77±11 in units of 10−4 cm3/s osmol cm2 basement membrane area. The transcellular water osmotic permeability is 32±7 (same units), leaving a paracellular contribution of 45±10 (same units). In the presence of 2.5 mM parachloromercuribenzenesulfonate (pCMBS) the apical permeability is reduced with an incubation of 10–15 min to 23% of its control value and the basolateral permeability to 8% of its control value (after 25 min) but the transepithelial permeability is only reduced to about 1/2 of the control value. This leaves a transcellular permeability of 6×10−4 cm3/s osmol cm2 of basement membrane area and a paracellular contribution of 33±6 (same units). These results indicate a significant contribution of the paracellular pathway to the transepithelial water osmotic permeabilities in PST.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00583732
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  • 9
    Electronic Resource
    Electronic Resource
    Diffusive water permeability in isolated kidney proximal tubular cells: Nature of the cellular water pathways (1988)
    Springer
    The journal of membrane biology 104 (1988), S. 35-43 
    Details
    ISSN: 1432-1424
    Keywords: diffusive water permeability ; kidney tubules ; water channels ; epithelia ; nuclear magnetic resonance (NMR) ; single-file diffusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The diffusive water permeability (P d ) of the plasma membrane of proximal kidney tubule cells was measured using a1H-NMR technique. The values obtained for the exchange time (T ex) across the membrane were independent of the cytocrit and of the Mn2+ concentration (in the range 2.5 to 5mm). At 25°C the calculatedP d value was (per cm2 of outer surface area without taking into account membrane invaginations) 197±17 μm/sec. This value equals 22.3±1.9 μm/sec when the invaginations are taken into account. Cell exposure to 2.5mm parachloromercuribenzenesulfonic acid,pCMBS, (for 20 to 35 min) reducedP d to 45% of its control value. Fivemm dithiothreitol, DTT, reverted this effect. The activation energy for the diffusive water flux was 5.2±1.0 kcal/mol under control conditions. It increased to 9.1±2.2 kcal/mol in the presence of 2.5mm pCMBS. Using our previous values for the osmotic water permeability (P os) in proximal straight tubular cells theP os/P d ratio equals 18±1, under control conditions, and 3.2±0.3 in the presence ofpCMBS. These experimental results indicate the presence of pathways for water, formed by proteins, crossing these membranes, which are closed bypCMBS. Assuming laminar flow (within the pore), fromP os/P d of 13 to 18 an unreasonably large pore radius of 12 to 15 Å is calculated which would not hinder cell entry of known extracellular markers. Alternatively, for a single-file pore, 11 to 20 would be the number of water molecules which would be in tandem inside the pore. The water permeability remaining in the presence ofpCMBS indicates water permeation through the lipid bilayer. There are similarities between these results and those obtained in human red blood cells and in the apical cell membrane of the toad urinary bladder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01871900
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