scholarly journals Cell volume and plasma membrane osmotic water permeability in epithelial cell layers measured by interferometry

1996 ◽  
Vol 71 (6) ◽  
pp. 3511-3522 ◽  
Author(s):  
J. Farinas ◽  
A.S. Verkman
Keyword(s):  
Plasma Membrane ◽  
Epithelial Cell ◽  
Cell Volume ◽  
Water Permeability ◽  
Osmotic Water Permeability ◽  
Osmotic Water ◽  
Cell Layers

scholarly journals Metformin, an AMPK activator, stimulates the phosphorylation of aquaporin 2 and urea transporter A1 in inner medullary collecting ducts

2016 ◽  
Vol 310 (10) ◽  
pp. F1008-F1012 ◽  
Author(s):  
Janet D. Klein ◽  
Yanhua Wang ◽  
Mitsi A. Blount ◽  
Patrick A. Molina ◽  
Lauren M. LaRocque ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
Water Permeability ◽  
Therapeutic Option ◽  
Apical Plasma Membrane ◽  
Osmotic Water Permeability ◽  
Urea Transporter ◽  
Aquaporin 2 ◽  
Urea Permeability ◽  
Osmotic Water ◽  
Collecting Ducts

Nephrogenic diabetes insipidus (NDI) is characterized by production of very large quantities of dilute urine due to an inability of the kidney to respond to vasopressin. Congenital NDI results from mutations in the type 2 vasopressin receptor (V2R) in ∼90% of families. These patients do not have mutations in aquaporin-2 (AQP2) or urea transporter UT-A1 (UT-A1). We tested adenosine monophosphate kinase (AMPK) since it is known to phosphorylate another vasopressin-sensitive transporter, NKCC2 (Na-K-2Cl cotransporter). We found AMPK expressed in rat inner medulla (IM). AMPK directly phosphorylated AQP2 and UT-A1 in vitro. Metformin, an AMPK activator, increased phosphorylation of both AQP2 and UT-A1 in rat inner medullary collecting ducts (IMCDs). Metformin increased the apical plasma membrane accumulation of AQP2, but not UT-A1, in rat IM. Metformin increased both osmotic water permeability and urea permeability in perfused rat terminal IMCDs. These findings suggest that metformin increases osmotic water permeability by increasing AQP2 accumulation in the apical plasma membrane but increases urea permeability by activating UT-A1 already present in the membrane. Lastly, metformin increased urine osmolality in mice lacking a V2R, a mouse model of congenital NDI. We conclude that AMPK activation by metformin mimics many of the mechanisms by which vasopressin increases urine-concentrating ability. These findings suggest that metformin may be a novel therapeutic option for congenital NDI due to V2R mutations.

scholarly journals Dynamic Changes in the Osmotic Water Permeability of Protoplast Plasma Membrane

2004 ◽  
Vol 135 (4) ◽  
pp. 2301-2317 ◽  
Author(s):  
Menachem Moshelion ◽  
Nava Moran ◽  
François Chaumont
Keyword(s):  
Plasma Membrane ◽  
Water Permeability ◽  
Osmotic Water Permeability ◽  
Dynamic Changes ◽  
Osmotic Water

scholarly journals Role of multiple phosphorylation sites in the COOH-terminal tail of aquaporin-2 for water transport: evidence against channel gating

2009 ◽  
Vol 296 (3) ◽  
pp. F649-F657 ◽  
Author(s):  
Hanne B. Moeller ◽  
Nanna MacAulay ◽  
Mark A. Knepper ◽  
Robert A. Fenton
Keyword(s):  
Plasma Membrane ◽  
Water Transport ◽  
Water Permeability ◽  
Laser Scanning Microscopy ◽  
Apical Plasma Membrane ◽  
Phosphorylation Sites ◽  
Osmotic Water Permeability ◽  
Aquaporin 2 ◽  
Osmotic Water

Arginine vasopressin (AVP)-regulated phosphorylation of the water channel aquaporin-2 (AQP2) at serine 256 (S256) is essential for its accumulation in the apical plasma membrane of collecting duct principal cells. In this study, we examined the role of additional AVP-regulated phosphorylation sites in the COOH-terminal tail of AQP2 on protein function. When expressed in Xenopus laevis oocytes, prevention of AQP2 phosphorylation at S256A (S256A-AQP2) reduced osmotic water permeability threefold compared with wild-type (WT) AQP2-injected oocytes. In contrast, prevention of AQP2 single phosphorylation at S261 (S261A), S264 (S264A), and S269 (S269A), or all three sites in combination had no significant effect on water permeability. Similarly, oocytes expressing S264D-AQP2 and S269D-AQP2, mimicking AQP2 phosphorylated at these residues, had similar water permeabilities to WT-AQP2-expressing oocytes. The use of high-resolution confocal laser-scanning microscopy, as well as biochemical analysis demonstrated that all AQP2 mutants, with the exception of S256A-AQP2, had equal abundance in the oocyte plasma membrane. Correlation of osmotic water permeability relative to plasma membrane abundance demonstrated that lack of phosphorylation at S256, S261, S264, or S269 had no effect on AQP2 unit water transport. Similarly, no effect on AQP2 unit water transport was observed for the 264D and 269D forms, indicating that phosphorylation of the COOH-terminal tail of AQP2 is not involved in gating of the channel. The use of phosphospecific antibodies demonstrated that AQP2 S256 phosphorylation is not dependent on any of the other phosphorylation sites, whereas S264 and S269 phosphorylation depend on prior phosphorylation of S256. In contrast, AQP2 S261 phosphorylation is independent of the phosphorylation status of S256.

scholarly journals Relative CO2/NH3 selectivities of mammalian aquaporins 0–9

2013 ◽  
Vol 304 (10) ◽  
pp. C985-C994 ◽  
Author(s):  
R. Ryan Geyer ◽  
Raif Musa-Aziz ◽  
Xue Qin ◽  
Walter F. Boron
Keyword(s):  
Plasma Membrane ◽  
Water Permeability ◽  
Xenopus Oocytes ◽  
Video Microscopy ◽  
Osmotic Water Permeability ◽  
Permeability Ratio ◽  
Diverse Range ◽  
Surface Ph ◽  
Aquaporin 1 ◽  
Osmotic Water

Previous work showed that aquaporin 1 (AQP1), AQP4-M23, and AQP5 each has a characteristic CO2/NH3 and CO2/H2O permeability ratio. The goal of the present study is to characterize AQPs 0–9, which traffic to the plasma membrane when heterologously expressed in Xenopus oocytes. We use video microscopy to compute osmotic water permeability ( Pf) and microelectrodes to record transient changes in surface pH (ΔpHS) caused by CO2 or NH3 influx. Subtracting respective values for day-matched, H2O-injected control oocytes yields the channel-specific values Pf* and ΔpHS*. We find that Pf* is significantly >0 for all AQPs tested except AQP6. (ΔpHS*)CO2 is significantly >0 for AQP0, AQP1, AQP4-M23, AQP5, AQP6, and AQP9. (ΔpHS*)NH3 is >0 for AQP1, AQP3, AQP6, AQP7, AQP8, and AQP9. The ratio (ΔpHS*)CO2/ Pf* falls in the sequence AQP6 (∞) > AQP5 > AQP4-M23 > AQP0 ≅ AQP1 ≅ AQP9 > others (0). The ratio (ΔpHS*)NH3/ Pf* falls in the sequence AQP6 (∞) > AQP3 ≅ AQP7 ≅ AQP8 ≅ AQP9 > AQP1 > others (0). Finally, the ratio (ΔpHS*)CO2/(−ΔpHS*)NH3 falls in the sequence AQP0 (∞) ≅ AQP4-M23 ≅ AQP5 > AQP6 > AQP1 > AQP9 > AQP3 (0) ≅ AQP7 ≅ AQP8. The ratio (ΔpHS*)CO2/(−ΔpHS*)NH3 is indeterminate for both AQP2 and AQP4-M1. In summary, we find that mammalian AQPs exhibit a diverse range of selectivities for CO2 vs. NH3 vs. H2O. As a consequence, by expressing specific combinations of AQPs, cells could exert considerable control over the movements of each of these three substances.

scholarly journals Importance of the mercury-sensitive cysteine on function and routing of AQP1 and AQP2 in oocytes

1997 ◽  
Vol 273 (3) ◽  
pp. F451-F456 ◽  
Author(s):  
S. M. Mulders ◽  
J. P. Rijss ◽  
A. Hartog ◽  
R. J. Bindels ◽  
C. H. van Os ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Plasma Membrane ◽  
Water Transport ◽  
Water Permeability ◽  
Nephrogenic Diabetes Insipidus ◽  
Osmotic Water Permeability ◽  
Wild Type ◽  
Mutant Proteins ◽  
Osmotic Water ◽  
Structural Differences

To discriminate between water transport of of aquaporin-2 (AQP2) mutants in nephrogenic diabetes insipidus and that of an AQP2 molecule used to drag them to the oolemma, we investigated the mercury sensitivity of wild-type and AQP2 C181S proteins in oocytes. Incubation with HgCl2 inhibited the osmotic water permeability (Pf) of human (h) AQP2 by 40%, whereas inhibition of hAQP1 was 75%. Oocytes expressing hAQP1 C189S revealed a Pf comparable to wild-type hAQP1, but mercury sensitivity was lost. In contrast, no increase in Pf was obtained when hAQP2 C181S was expressed. Also, expression of rat AQP2 C181A and C181S mutants did not increase the Pf, which contrasts with published observations. Immunocytochemistry and immunoblotting revealed that only AQP1, AQP1 C189S, and AQP2 were targeted to the plasma membrane and that AQP2 mutant proteins are retarded in the endoplasmic reticulum. In conclusion, water transport through AQP2 is less sensitive to mercury inhibition than through AQP1. Furthermore, substitution of the mercury-sensitive cysteine for a serine results in an impaired routing of human and rat AQP2. Similar mutations have no effect on AQP1 function, which is indicative of structural differences between AQP1 and AQP2.

scholarly journals Osmotic water permeability of human red cells.

1981 ◽  
Vol 77 (5) ◽  
pp. 549-570 ◽  
Author(s):  
T C Terwilliger ◽  
A K Solomon
Keyword(s):  
Systematic Error ◽  
Water Permeability ◽  
Perturbation Technique ◽  
Mean Value ◽  
Red Cells ◽  
Osmotic Water Permeability ◽  
Osmotic Water ◽  
New Perturbation ◽  
The Relationship ◽  
Human Red Cells

The osmotic water permeability of human red cells has been reexamined with a stopped-flow device and a new perturbation technique. Small osmotic gradients are used to minimize the systematic error caused by nonlinearities in the relationship between cell volume and light scattering. Corrections are then made for residual systematic error. Our results show that the hydraulic conductivity, Lp, is essentially independent of the direction of water flow and of osmolality in the range 184-365 mosM. the mean value of Lp obtained obtained was 1.8 +/- 0.1 (SEM) X 10-11 cm3 dyne -1 s-1.

Cell osmotic water permeability of isolated rabbit proximal straight tubules

1982 ◽  
Vol 242 (4) ◽  
pp. F321-F330 ◽  
Author(s):  
E. Gonzalez ◽  
P. Carpi-Medina ◽  
G. Whittembury
Keyword(s):  
Surface Area ◽  
Water Flow ◽  
Water Permeability ◽  
Permeability Coefficient ◽  
Osmotic Water Permeability ◽  
Water Permeability Coefficient ◽  
Osmotic Water ◽  
Straight Tubules ◽  
Tubular Surface ◽  
Set Up

Proximal straight tubules were dissected and mounted in a chamber with their lumina occluded. The well-stirred bath could be 95% changed within 84 ms to set up osmotic gradients (delta Coi) across the peritubular cell aspect. Volume changes (less than or equal to 10 pl/mm) were estimated from continuous records of diameter changes (error less than 0.1 micrometers). delta Coi greater than or equal to 2-3 mosM could be discerned. delta Coi values from 10 to 44 mosM were used to evaluate Posc, the cell osmotic water permeability coefficient, and extrapolated to delta Coi = 0. Posc = 25.1 (+/- 2.3) X 10(-4) cm3.s-1.osM-1.cm2 tubular surface area-1. These values are lower than those reported for Pose, the transepithelial osmotic water permeability coefficient, and become lower if corrected for the real (infolded) peritubular cell surface area. Thus, for a given osmotic difference, transcellular water flow finds a higher resistance than paracellular water flow. Experiments were also performed with delta Coi greater than 100 mosM, but interpretation of these data is difficult because of the presence of volume regulatory phenomena and other undesirable effects.

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