Water transport across mammalian cell membranes

1996 ◽  
Vol 270 (1) ◽  
pp. C12-C30 ◽  
Author(s):  
A. S. Verkman ◽  
A. N. van Hoek ◽  
T. Ma ◽  
A. Frigeri ◽  
W. R. Skach ◽  
...  
Keyword(s):  
Water Transport ◽  
Cell Membranes ◽  
Water Channel ◽  
Water Channels ◽  
Channel Structure ◽  
Level Information ◽  
Selective Channel ◽  
Transcriptional Units ◽  
Measurement Strategies

This review summarizes recent progress in water-transporting mechanisms across cell membranes. Modern biophysical concepts of water transport and new measurement strategies are evaluated. A family of water-transporting proteins (water channels, aquaporins) has been identified, consisting of small hydrophobic proteins expressed widely in epithelial and nonepithelial tissues. The functional properties, genetics, and cellular distributions of these proteins are summarized. The majority of molecular-level information about water-transporting mechanisms comes from studies on CHIP28, a 28-kDa glycoprotein that forms tetramers in membranes; each monomer contains six putative helical domains surrounding a central aqueous pathway and functions independently as a water-selective channel. Only mutations in the vasopressin-sensitive water channel have been shown to cause human disease (non-X-linked congenital nephrogenic diabetes insipidus); the physiological significance of other water channels remains unproven. One mercurial-insensitive water channel has been identified, which has the unique feature of multiple overlapping transcriptional units. Systems for expression of water channel proteins are described, including Xenopus oocytes, mammalian and insect cells, and bacteria. Further work should be directed at elucidation of the role of water channels in normal physiology and disease, molecular analysis of regulatory mechanisms, and water channel structure determination at atomic resolution.

Water transport in maize roots under the influence of mercuric chloride and water stress: a role of water channels

2006 ◽  
Vol 50 (1) ◽  
pp. 74-80 ◽  
Author(s):  
I. F. Ionenko ◽  
A. V. Anisimov ◽  
F. G. Karimova
Keyword(s):  
Water Stress ◽  
Water Transport ◽  
Mercuric Chloride ◽  
Water Channels ◽  
Maize Roots

Water transport across plant tissue: Role of water channels

1997 ◽  
Vol 89 (5-6) ◽  
pp. 259-273 ◽  
Author(s):  
Ernst Steudle
Keyword(s):  
Water Transport ◽  
Plant Tissue ◽  
Water Channels

Nature of ADH-Induced Endosomes In Toad Urinary Bladder Granular Epithelial Cells

1998 ◽  
Vol 4 (S2) ◽  
pp. 1034-1035
Author(s):  
A.J. Mia ◽  
L.X. Oakford ◽  
A. Dibas ◽  
T. Yorio
Keyword(s):  
Urinary Bladder ◽  
Water Channel ◽  
Water Channels ◽  
Toad Urinary Bladder ◽  
Multivesicular Bodies ◽  
Osmotic Gradient ◽  
True Nature ◽  
Golgi Bodies ◽  
Glass Tubes

Serosal ADH stimulation enhances water flow under an imposed osmotic gradient through insertion of water channels (aggrephores) into the mucosal plasma membrane of toad urinary bladder sacs. Following cessation of ADH actions, water channels are retrieved as endosomes that can be visualized by mucosal inclusion of horseradish peroxidase (HRP) into round vesicles, long tubules and multivesicular bodies within the cytosol (1,2,3). Endosomes also occur adjacent to golgi bodies or lysosomes (1,2,3). However, true nature of endosomes including their formation at the mucosal surface and their shuttling in granular cells is still unclear (4,5). Current studies were undertaken to understand the role of endosomes in water channel cycling in this renal membrane model.Urinary bladder sacs removed surgically from doubly-pithed toads, were suspended at ends of glass tubes. Control (no hormone) and experimental bladder sacs were exposed to ADH for 10 min in the absence of osmotic gradient.

Salt and water transport across alveolar and distal airway epithelia in the adult lung

1996 ◽  
Vol 270 (4) ◽  
pp. L487-L503 ◽  
Author(s):  
M. A. Matthay ◽  
H. G. Folkesson ◽  
A. S. Verkman
Keyword(s):  
Water Transport ◽  
Water Permeability ◽  
Fluid Transport ◽  
Water Channels ◽  
Molecular Water ◽  
Alveolar Epithelial ◽  
Distal Airway ◽  
Injured Lung

Substantial progress has been made in understanding the role of the distal airway and alveolar epithelial barriers in regulating lung fluid balance. Molecular, cellular, and whole animal studies have demonstrated that reabsorption of fluid from the distal air spaces of the lung is driven by active sodium transport. Several different in vivo, in situ, and isolated lung preparations have been used to study the mechanisms that regulate fluid transport in the normal and injured lung. Catecholamine-dependent and -independent regulatory mechanisms have been identified that modulate fluid transport, probably by acting on apical sodium channel uptake or the activity of the Na, K-ATPase pumps. Recently, a family of molecular water channels (aquaporins) has been identified that are small (approximately 30 kDa) integral membrane proteins expressed widely in fluid-transporting epithelia and endothelia. At present, four different water channels have been identified in trachea and lung. Measurements of osmotic water permeability in in situ perfused lung and isolated perfused airways suggest a significant contribution of these molecular water channels to measured water permeability. However, further studies are required to determine the role of these water channels in normal pulmonary physiology and disease. Recent studies have provided new insights into the role of the alveolar epithelial barrier in clinical and experimental acute lung injury. Unlike the lung endothelium, the alveolar epithelium is resistant to several clinically relevant types of injury, including endotoxemia and bacteremia as well as aspiration of hyperosmolar solutions. In addition, even when the alveolar barrier has been injured, its capacity to transport edema fluid from the distal air spaces of the lung recovers rapidly. Future studies need to integrate new insights into the molecular mechanisms of alveolar epithelial sodium and water transport with functional studies in the normal and injured lung.

scholarly journals Tetrameric assembly of CHIP28 water channels in liposomes and cell membranes: a freeze-fracture study.

1993 ◽  
Vol 123 (3) ◽  
pp. 605-618 ◽  
Author(s):  
J M Verbavatz ◽  
D Brown ◽  
I Sabolić ◽  
G Valenti ◽  
D A Ausiello ◽  
...  
Keyword(s):  
Water Permeability ◽  
Cho Cells ◽  
Cell Membranes ◽  
Plasma Membranes ◽  
Single Channel ◽  
Water Channel ◽  
Freeze Fracture ◽  
Water Channels ◽  
Straight Tubules ◽  
Tetrameric Assembly

Channel forming integral protein of 28 kD (CHIP28) functions as a water channel in erythrocytes, kidney proximal tubule and thin descending limb of Henle. CHIP28 morphology was examined by freeze-fracture EM in proteoliposomes reconstituted with purified CHIP28, CHO cells stably transfected with CHIP28k cDNA, and rat kidney tubules. Liposomes reconstituted with HPLC-purified CHIP28 from human erythrocytes had a high osmotic water permeability (Pf0.04 cm/s) that was inhibited by HgCl2. Freeze-fracture replicas showed a fairly uniform set of intramembrane particles (IMPs); no IMPs were observed in liposomes without incorporated protein. By rotary shadowing, the IMPs had a diameter of 8.5 +/- 1.3 nm (mean +/- SD); many IMPs consisted of a distinct arrangement of four smaller subunits surrounding a central depression. IMPs of similar size and appearance were seen on the P-face of plasma membranes from CHIP28k-transfected (but not mock-transfected) CHO cells, rat thin descending limb (TDL) of Henle, and S3 segment of proximal straight tubules. A distinctive network of complementary IMP imprints was observed on the E-face of CHIP28-containing plasma membranes. The densities of IMPs in the size range of CHIP28 IMPs, determined by non-linear regression, were (in IMPs/microns 2): 2,494 in CHO cells, 5,785 in TDL, and 1,928 in proximal straight tubules; predicted Pf, based on the CHIP28 single channel water permeability of 3.6 x 10(-14) cm3/S (10 degrees C), was in good agreement with measured Pf of 0.027 cm/S, 0.075 cm/S, and 0.031 cm/S, respectively, in these cell types. Assuming that each CHIP28 monomer is a right cylindrical pore of length 5 nm and density 1.3 g/cm3, the monomer diameter would be 3.2 nm; a symmetrical arrangement of four cylinders would have a greatest diameter of 7.2 nm, which after correction for the thickness of platinum deposit, is similar to the measured IMP diameter of approximately 8.5 nm. These results provide a morphological signature for CHIP28 water channels and evidence for a tetrameric assembly of CHIP28 monomers in reconstituted proteoliposomes and cell membranes.

Water transport and cell survival in cryobiological procedures

1977 ◽  
Vol 278 (959) ◽  
pp. 191-205 ◽  
Keyword(s):  
Cell Survival ◽  
Water Transport ◽  
Cell Membranes ◽  
Living Cells ◽  
Phase Changes ◽  
Basic Information ◽  
Freezing And Thawing ◽  
Temperature Changes ◽  
Cooling Procedure

Living cells may be cooled to 77 K (liquid nitrogen) either to destroy them selectively or to store them for long periods. Water transport across the cell membranes during freezing and thawing is a primary factor determining whether the cells survive. These water movements are controlled by phase changes both intracellular and extracellular and by other factors such as the nature of any cryoprotective agent present, and the rates of cooling and thawing. The relation between cooling procedure, water transport and cell survival is discussed. In particular, the crucial role of dilution shock is emphasized : this is the damage to cells induced during the dilution that occurs both as ice melts during rewarming and when any cryoprotective additives are removed after thawing. Apart from the usefulness of understanding these processes for maximizing preservation or controlling selective destruction, the diverse responses of cells to different combinations of water transport and temperature changes appear likely to provide basic information on the properties of cell membranes.

scholarly journals Lessons on Renal Physiology from Transgenic Mice Lacking Aquaporin Water Channels

1999 ◽  
Vol 10 (5) ◽  
pp. 1126-1135
Author(s):  
A. S. VERKMAN
Keyword(s):  
Proximal Tubule ◽  
Knockout Mice ◽  
Collecting Duct ◽  
Water Channel ◽  
Water Channels ◽  
Renal Physiology ◽  
Vasa Recta ◽  
Phenotype Analysis ◽  
Type Water

Abstract. Several aquaporin-type water channels are expressed in kidney: AQP1 in the proximal tubule, thin descending limb of Henle, and vasa recta; AQP2, AQP3, and AQP4 in the collecting duct; AQP6 in the papilla; and AQP7 in the proximal tubule. AQP2 is the vasopressin-regulated water channel that is important in hereditary and acquired diseases affecting urine-concentrating ability. It has been difficult to establish the roles of the other aquaporins in renal physiology because suitable aquaporin inhibitors are not available. One approach to the problem has been to generate and analyze transgenic knockout mice in which individual aquaporins have been selectively deleted by targeted gene disruption. Phenotype analysis of kidney and extrarenal function in knockout mice has been very informative in defining the role of aquaporins in organ physiology and addressing basic questions regarding the route of transepithelial water transport and the mechanism of near isoosmolar fluid reabsorption. This article describes new renal physiologic insights revealed by phenotype analysis of aquaporin-knockout mice and the prospects for further basic and clinical developments.

Aquaporin-1 in plasma membrane and caveolae provides mercury-sensitive water channels across lung endothelium

1996 ◽  
Vol 270 (1) ◽  
pp. H416-H422 ◽  
Author(s):  
J. E. Schnitzer ◽  
P. Oh
Keyword(s):  
Endothelial Cell ◽  
Cell Surface ◽  
Water Transport ◽  
Plasma Membranes ◽  
Tritiated Water ◽  
Water Channel ◽  
Water Channels ◽  
Transcellular Transport ◽  
Aquaporin 1 ◽  
Rat Lungs

Classically, water transport across endothelium of the continuous type found in the microvessels of many organs such as lung was thought to occur almost completely via the paracellular pathway through intercellular junctions. Direct transmembrane and transcellular transport was considered to be minimal. In this study, we focused on the critical transport interface in direct contact with the circulating blood by purifying luminal endothelial cell plasma membranes directly from rat lungs and then isolating the noncoated plasmalemmal vesicles or caveolae from these membranes. Immunoblotting of these fractions showed that the transmembrane water channel protein aquaporin-1 was amply expressed on the endothelial cell surface at levels comparable to rat erythrocyte plasma membranes. It was found concentrated, but not exclusively, in caveolae. The functional role of these water channels in transport was examined in rat lungs perfused in situ with tritiated water by testing known inhibitors of aquaporin-1-mediated transmembrane water transport. Mercurial sulfhydryl reagents such as HgCl2 reversibly reduced tritiated water uptake without affecting small solute transport. Just like certain epithelia, endothelia might express physiologically relevant amounts of aquaporin-1 on their cell surface to permit direct, mercurial-sensitive, transcellular transport of water.

Neuromyelitis optica spectrum: novel concept of pathogenesis, diagnosis and treatment of Devic’s disease

2009 ◽  
Vol 150 (46) ◽  
pp. 2101-2109 ◽  
Author(s):  
Péter Csécsei ◽  
Anita Trauninger ◽  
Sámuel Komoly ◽  
Zsolt Illés
Keyword(s):  
Neuromyelitis Optica ◽  
Water Channel ◽  
Diagnostic Procedures ◽  
Diagnosis And Treatment ◽  
Clinical Settings ◽  
Permanent Disability ◽  
Therapeutic Decisions ◽  
Novel Concept ◽  
The Brain

The identification of autoantibodies generated against the brain isoform water channel aquaporin4 in the sera of patients, changed the current diagnostic guidelines and concept of neuromyelitis optica (NMO). In a number of cases, clinical manifestation is spatially limited to myelitis or relapsing optic neuritis creating a diverse. NMO spectrum. Since prevention of relapses provides the only possibility to reduce permanent disability, early diagnosis and treatment is mandatory. In the present study, we discuss the potential role of neuroimaging and laboratory tests in differentiating the NMO spectrum from other diseases, as well as the diagnostic procedures and therapeutic options. We also present clinical cases, to provide examples of different clinical settings, diagnostic procedures and therapeutic decisions.

Sign in / Sign up

Export Citation Format

Share Document