scholarly journals Water transport in neonatal and adult rabbit proximal tubules

2002 ◽  
Vol 283 (2) ◽  
pp. F280-F285 ◽  
Author(s):  
Raymond Quigley ◽  
Michel Baum
Keyword(s):  
Water Transport ◽  
Water Permeability ◽  
Water Movement ◽  
Chloride Transport ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Proximal Tubules ◽  
Adult Rabbit ◽  
Osmotic Gradient ◽  
Intracellular Compartment

We have recently demonstrated that although the osmotic water permeability ( P f) of neonatal proximal tubules is higher than that of adult tubules, the P f of brush-border and basolateral membrane vesicles from neonatal rabbits is lower than that of adults. The present study examined developmental changes in the water transport characteristics of proximal convoluted tubules (PCTs) in neonatal (9–16 days old) and adult rabbits to determine whether the intracellular compartment or paracellular pathway is responsible for the maturational difference in transepithelial water transport. The permeability of n-butanol was higher in the neonatal PCT than the adult PCT at all temperatures examined, whereas the diffusional water permeability was identical. Increasing the osmotic gradient increased volume absorption in both the neonatal and the adult PCT to the same degree. The P f was not different between the neonatal and the adult PCT at any osmotic gradient studied. To assess solvent drag as a measure of the paracellular transport of water, the effect of the osmotic gradient on mannitol and chloride transport were measured. There was no change in chloride or mannitol transport with the increased osmotic gradient in either group, indicating that there was no detectable paracellular water movement. In addition, the mannitol permeability of the neonatal PCT was found to be lower than that of the adult PCT with the isotonic bath (8.97 ± 4.01 vs. 40.49 ± 13.89 μm/s, P < 0.05). Thus the intracellular compartment of the neonatal PCT has a lower resistance for water transport than the adult PCT and is responsible for the higher than expected P f in the neonatal PCT.

Developmental changes in rabbit juxtamedullary proximal convoluted tubule water permeability

1996 ◽  
Vol 271 (4) ◽  
pp. F871-F876 ◽  
Author(s):  
R. Quigley ◽  
M. Baum
Keyword(s):  
Proximal Tubule ◽  
Water Transport ◽  
Water Permeability ◽  
Water Movement ◽  
Adult Rabbit ◽  
Osmotic Water ◽  
Glomerular Filtrate ◽  
Convoluted Tubules ◽  
Insight Into

The mammalian proximal tubule reabsorbs the bulk of the glomerular filtrate in a nearly isosmotic fashion due to the high osmotic water permeability (Pf) of this segment. Although the characteristics of proximal tubule water transport have been studied in the adult proximal tubule, little is known about the neonatal segment. The present study directly measured the Pf and diffusional water permeability (PDW) of neonatal (10 +/- 2 day old) and adult rabbit juxtamedullary proximal convoluted tubules (PCT) using in vitro microperfusion. The Pf of neonatal juxtamedullary PCT was greater than the Pf of adult juxtamedullary PCT. In contrast, the PDW was not different between the two groups. The Pf and PDW values of both neonatal and adult tubules were inhibited to the same degree by p-chloromercuribenzene sulfonate and had identical activation energies. The transepithelial reflection coefficients of NaCl and NaHCO3 were also found to be similar in both the neonatal and adult proximal tubules. Thus neonatal and adult juxtamedullary PCT have many characteristics of water transport that are identical; however, neonatal Pf is three to five times that of the adult value. This difference in Pf with identical PDW values may give an insight into the transepithelial pathway for water movement in the neonatal tubule.

Chloride Transport Across Rat Ileal Basolateral Membrane Vesicles

1992 ◽  
Vol 201 (3) ◽  
pp. 254-260 ◽  
Author(s):  
M. Daher ◽  
S. Acra ◽  
W. Dykes ◽  
F. K. Ghishan
Keyword(s):  
Chloride Transport ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Basolateral Membrane Vesicles

Reduced osmotic water permeability of the peritoneal barrier in aquaporin-1 knockout mice

1999 ◽  
Vol 276 (1) ◽  
pp. C76-C81 ◽  
Author(s):  
Baoxue Yang ◽  
Hans G. Folkesson ◽  
Jian Yang ◽  
Michael A. Matthay ◽  
Tonghui Ma ◽  
...  
Keyword(s):  
Water Transport ◽  
Peritoneal Cavity ◽  
Knockout Mice ◽  
Fluid Transport ◽  
Water Movement ◽  
Osmotic Gradient ◽  
Half Time ◽  
Aquaporin 1 ◽  
Osmotic Water ◽  
Major Route

Aquaporin-1 (AQP1) water channels are expressed widely in epithelia and capillary endothelia involved in fluid transport. To test whether AQP1 facilitates water movement from capillaries into the peritoneal cavity, osmotically induced water transport rates were compared in AQP1 knockout [(−/−)], heterozygous [(+/−)], and wild-type [(+/+)] mice. In (+/+) mice, RT-PCR showed detectable transcripts for AQP1, AQP3, AQP4, AQP7, and AQP8. Immunofluorescence showed AQP1 protein in capillary endothelia and mesangium near the peritoneal surface and AQP4 in adherent muscle plasmalemma. For measurement of water transport, 2 ml of saline containing 300 mM sucrose (600 mosM) were infused rapidly into the peritoneal cavity via a catheter. Serial fluid samples (50 μl) were withdrawn over 60 min, with albumin as a volume marker. The albumin dilution data showed significantly decreased initial volume influx in AQP1 (−/−) mice: 101 ± 8, 107 ± 5, and 42 ± 4 (SE) μl/min in (+/+), (+/−), and (−/−) mice, respectively [ n = 6–10, P < 0.001, (−/−) vs. others]. Volume influx for AQP4 knockout mice was 100 ± 8 μl/min. In the absence of an osmotic gradient,3H2O uptake [half time = 2.3 and 2.2 min in (+/+) and (−/−) mice, respectively], [14C]urea uptake [half time = 7.9 and 7.7 min in (+/+) and (−/−) mice, respectively], and spontaneous isosmolar fluid absorption from the peritoneal cavity [0.47 ± 0.05 and 0.46 ± 0.04 ml/h in (+/+) and (−/−) mice, respectively] were not affected by AQP1 deletion. Therefore, AQP1 provides a major route for osmotically driven water transport across the peritoneal barrier in peritoneal dialysis.

Intracellular pH, transepithelial pH gradients, and ADH-induced water channels

1983 ◽  
Vol 244 (6) ◽  
pp. F712-F718 ◽  
Author(s):  
M. Parisi ◽  
J. Wietzerbin ◽  
J. Bourguet
Keyword(s):  
Intracellular Ph ◽  
Water Permeability ◽  
Water Movement ◽  
Ph Regulation ◽  
Pivotal Role ◽  
Osmotic Gradient ◽  
Bicarbonate Buffer ◽  
Ph Gradients ◽  
Intracellular Ph Regulation ◽  
Cellular Acidification

Urinary bladders of frogs were exposed to a transepithelial proton and osmotic gradient (serosal pH 8.1, Tris or bicarbonate buffer; mucosal pH 5.8, unbuffered) while the alkalinization rate of the mucosal bath and the net water movement were simultaneously monitored. It was observed that 1) the mucosal alkalinization rate was dependent on serosal pH and buffer; 2) oxytocin increased the mucosal alkalinization rate only when serosal bicarbonate was employed, whereas the net water movement augmented both when serosal bicarbonate or Tris buffers were used; 3) amiloride did not modify the mucosal alkalinization rate either before or after oxytocin; 4) the increases in the mucosal alkalinization rate and in the net water movement induced by oxytocin (serosal bicarbonate) were negatively correlated. In other experiments intracellular pH (pHi) was estimated with the DMO distribution technique with the following results. 1) Oxytocin increased the pHi when either serosal bicarbonate or Tris buffers was used and even in the presence of a low mucosal pH (Tris buffer, pH 5.8). 2) Important cellular acidification was observed when CO2 was bubbled (to pH 5.8), whereas the hydrosmotic response to 8-bromo-cAMP was clearly inhibited. These results indicate that cellular alkalinization could play a pivotal role in action of ADH, show that ADH can modify the transepithelial pH equilibrium mechanism, and suggest that intracellular pH regulation and water permeability control can be linked regulatory processe.

Luminal and basolateral uptake and receptor binding of IGF-I in rabbit renal proximal tubules

1993 ◽  
Vol 265 (5) ◽  
pp. F624-F633 ◽  
Author(s):  
A. Flyvbjerg ◽  
S. Nielsen ◽  
M. I. Sheikh ◽  
C. Jacobsen ◽  
H. Orskov ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Dissociation Constants ◽  
Basolateral Membrane ◽  
Membrane Vesicles ◽  
Proximal Tubules ◽  
Asymmetric Distribution ◽  
Basolateral Membrane Vesicles ◽  
Electron Microscope Autoradiography ◽  
Microscope Autoradiography ◽  
Igf I

The aim of the present study was to quantify and compare the luminal and basolateral binding and uptake of 125I-labeled insulin-like growth factor I (IGF-I) by means of 1) isolated, perfused, proximal tubules combined with electron microscope autoradiography and 2) luminal and basolateral membrane vesicles from rabbit proximal tubules. 125I-IGF-I was added to isolated perfused proximal tubules for 30 min in concentrations of 1.6-3.9 micrograms/l to either the perfusate or the bath. The luminal and basolateral uptake in 30 min averaged 447 and 410 fg/mm, respectively. About 20% of the luminally absorbed IGF-I was digested. Addition of excess unlabeled IGF-I (10(-7) M) to the bath produced complete inhibition of the basolateral binding/uptake, whereas no inhibition of the luminal uptake was seen. Electron microscope autoradiography showed that IGF-I after luminal endocytic uptake to a large extent was transported into lysosomes. After basolateral exposure the major portion of the grains was found over the basolateral cell membrane; however, a significant amount was located over endocytic vacuoles and lysosomes in both apical and basal parts of the cells. In both luminal and basolateral membrane vesicles, single-class, high-affinity binding sites for IGF-I were found with dissociation constants of 6.3 and 5.7 nM, respectively. Specific binding capacities averaged 2.7 and 25.7 pmol IGF-I/mg protein in luminal and basolateral vesicles. The biochemical data suggest an asymmetric distribution of specific IGF-I receptors in the luminal and basolateral membranes, with a greater abundance of receptors in the latter. The extensive basolateral endocytic binding/uptake of IGF-I compared with that of the luminal in isolated perfused tubules differs considerably from the processing of other peptide hormones.

SPI-0211 activates T84 cell chloride transport and recombinant human ClC-2 chloride currents

2004 ◽  
Vol 287 (5) ◽  
pp. C1173-C1183 ◽  
Author(s):  
John Cuppoletti ◽  
Danuta H. Malinowska ◽  
Kirti P. Tewari ◽  
Qiu-ju Li ◽  
Ann M. Sherry ◽  
...  
Keyword(s):  
Apical Membrane ◽  
Chloride Transport ◽  
Short Circuit ◽  
Basolateral Membrane ◽  
Adult Rabbit ◽  
Dependent Manner ◽  
T84 Cells ◽  
Hek 293 ◽  
Hek 293 Cells ◽  
293 Cells

The purpose of this study was to determine the mechanism of action of SPI-0211 (lubiprostone), a novel bicyclic fatty acid in development for the treatment of bowel dysfunction. Adult rabbit intestine was shown to contain mRNA for ClC-2 using RT-PCR, Northern blot analysis, and in situ hybridization. T84 cells grown to confluence on permeable supports were shown to express ClC-2 channel protein in the apical membrane. SPI-0211 increased electrogenic Cl− transport across the apical membrane of T84 cells, with an EC50 of ∼18 nM measured by short-circuit current ( Isc) after permeabilization of the basolateral membrane with nystatin. SPI-0211 effects on Cl− currents were also measured by whole cell patch clamp using the human embryonic kidney (HEK)-293 cell line stably transfected with either recombinant human ClC-2 or recombinant human cystic fibrosis transmembrane regulator (CFTR). In these studies, SPI-0211 activated ClC-2 Cl− currents in a concentration-dependent manner, with an EC50 of ∼17 nM, and had no effect in nontransfected HEK-293 cells. In contrast, SPI-0211 had no effect on CFTR Cl− channel currents measured in CFTR-transfected HEK-293 cells. Activation of ClC-2 by SPI-0211 was independent of PKA. Together, these studies demonstrate that SPI-0211 is a potent activator of ClC-2 Cl− channels and suggest a physiologically relevant role for ClC-2 Cl− channels in intestinal Cl− transport after SPI-0211 administration.

Diluting segment in avian kidney. II. Water and chloride transport

1986 ◽  
Vol 250 (3) ◽  
pp. R341-R347 ◽  
Author(s):  
T. Miwa ◽  
H. Nishimura
Keyword(s):  
Water Permeability ◽  
Chloride Transport ◽  
Arginine Vasotocin ◽  
Osmotic Gradient ◽  
Thick Ascending Limb ◽  
Osmotic Water Permeability ◽  
Diluting Segment ◽  
Henle's Loop ◽  
Osmotic Water ◽  
Avian Kidney

The mammalian-type nephrons of avian kidneys contain a Henle's loop that runs parallel to the collecting ducts and the vasa recta. Thus we examined whether the thick ascending limb (TAL) of Henle's loop of the avian kidney acts as a diluting segment by measuring water and Cl transport in the isolated and perfused TAL of the quail, Coturnix coturnix. The TAL showed a lumen-positive transepithelial voltage (Vt) (+9.4 +/- 0.4 mV, n = 28). Net water flux (Jv) was nearly zero when the TAL was perfused and bathed with isosmotic solution. When the osmotic gradient was imposed, Jv increased only slightly, and thus the osmotic water permeability (Lp) was low. Arginine vasotocin (AVT) added to the hyperosmotic bath did not alter either Jv, Lp, or Vt. Cl efflux (lumen to bath, 370.4 +/- 27.7 peq X mm-1 X min-1) was higher than Cl influx (bath to lumen, 98.6 +/- 14.3 peq X mm-1 X min-1) when measured in the different tubules. AVT showed no effect on Cl efflux. These results indicate that in the TAL of the quail osmotic water permeability is low while net Cl reabsorption is present, suggesting that the TAL functions as a diluting segment.

Knockdown of hepatocyte aquaporin-8 by RNA interference induces defective bile canalicular water transport

2009 ◽  
Vol 296 (1) ◽  
pp. G93-G100 ◽  
Author(s):  
M. Cecilia Larocca ◽  
Leandro R. Soria ◽  
M. Victoria Espelt ◽  
Guillermo L. Lehmann ◽  
Raúl A. Marinelli
Keyword(s):  
Rna Interference ◽  
Water Transport ◽  
Hepg2 Cells ◽  
Water Movement ◽  
Rat Hepatocytes ◽  
Conclusive Evidence ◽  
Osmotic Gradient ◽  
Bile Formation ◽  
Canalicular Membrane ◽  
Water Secretion

Aquaporin-8 (AQP8) water channels, which are expressed in rat hepatocyte bile canalicular membranes, are involved in water transport during bile formation. Nevertheless, there is no conclusive evidence that AQP8 mediates water secretion into the bile canaliculus. In this study, we directly evaluated whether AQP8 gene silencing by RNA interference inhibits canalicular water secretion in the human hepatocyte-derived cell line, HepG2. By RT-PCR and immunoblotting we found that HepG2 cells express AQP8 and by confocal immunofluorescence microscopy that it is localized intracellularly and on the canalicular membrane, as described in rat hepatocytes. We also verified the expression of AQP8 in normal human liver. Forty-eight hours after transfection of HepG2 cells with RNA duplexes targeting two different regions of human AQP8 molecule, the levels of AQP8 protein specifically decreased by 60–70%. We found that AQP8 knockdown cells showed a significant decline in the canalicular volume of ∼70% ( P < 0.01), suggesting an impairment in the basal (nonstimulated) canalicular water movement. We also found that the decreased AQP8 expression inhibited the canalicular water transport in response either to an inward osmotic gradient (−65%, P < 0.05) or to the bile secretory agonist dibutyryl cAMP (−80%, P < 0.05). Our data suggest that AQP8 plays a major role in water transport across canalicular membrane of HepG2 cells and support the notion that defective expression of AQP8 causes bile secretory dysfunction in human hepatocytes.

scholarly journals Angulin-1 (LSR) Affects Paracellular Water Transport, However Only in Tight Epithelial Cells

2021 ◽  
Vol 22 (15) ◽  
pp. 7827
Author(s):  
Carlos Ayala-Torres ◽  
Susanne M. Krug ◽  
Rita Rosenthal ◽  
Michael Fromm
Keyword(s):  
Epithelial Cell ◽  
Epithelial Cells ◽  
Water Transport ◽  
Cell Lines ◽  
Water Permeability ◽  
Water Flux ◽  
Epithelial Cell Line ◽  
Osmotic Gradient ◽  
The Impact ◽  
Ht 29

Water transport in epithelia occurs transcellularly (aquaporins) and paracellularly (claudin-2, claudin-15). Recently, we showed that downregulated tricellulin, a protein of the tricellular tight junction (tTJ, the site where three epithelial cells meet), increased transepithelial water flux. We now check the hypothesis that another tTJ-associated protein, angulin-1 (alias lipolysis-stimulated lipoprotein receptor, LSR) is a direct negative actuator of tTJ water permeability depending on the tightness of the epithelium. For this, a tight and an intermediate-tight epithelial cell line, MDCK C7 and HT-29/B6, were stably transfected with CRISPR/Cas9 and single-guide RNA targeting angulin-1 and morphologically and functionally characterized. Water flux induced by an osmotic gradient using 4-kDa dextran caused water flux to increase in angulin-1 KO clones in MDCK C7 cells, but not in HT-29/B6 cells. In addition, we found that water permeability in HT-29/B6 cells was not modified after either angulin-1 knockout or tricellulin knockdown, which may be related to the presence of other pathways, which reduce the impact of the tTJ pathway. In conclusion, modulation of the tTJ by knockout or knockdown of tTJ proteins affects ion and macromolecule permeability in tight and intermediate-tight epithelial cell lines, while the transepithelial water permeability was affected only in tight cell lines.

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