Importance of molecular size and hydrogen bonding in vasopressin-stimulated urea transport

1982 ◽  
Vol 243 (1) ◽  
pp. C27-C34 ◽  
Author(s):  
R. J. Petrucelli ◽  
P. Eggena
Keyword(s):  
Hydrogen Bonding ◽  
Water Flow ◽  
Transport Mechanism ◽  
Tritiated Water ◽  
Molecular Size ◽  
Urea Transport ◽  
Acid Transport ◽  
Glutaraldehyde Fixation ◽  
Osmotic Water ◽  
Osmotic Water Flow

We have employed a variety of urea and thiourea analogues to elucidate further the vasopressin-stimulated urea transport mechanism. In the urea series there was a progressive inhibition of tracer urea transport as cylindrical radius of analogue increased from 2.9 to 3.5 A. Above 3.8 A no inhibition was found. Thiourea analogues were more potent inhibitors for comparable cylindrical radii, and compounds greater than 3.8 A again were not inhibitory. Inhibition was comparable when the inhibitor was moving in the same or opposite directions. Urea transport and its inhibition were preserved in bladders fixed with glutaraldehyde. Osmotic water flow, tritiated water flow, and uric acid transport were not affected by any analogues tested. Analogues of urea and thiourea affected the transport of labeled methylurea and thiourea in a manner similar to their effect on urea. We therefore propose that the urea transport mechanism is a channel with a cylindrical radius between 3.5 and 3.8 A that is capable of interaction with the moving species by hydrogen bonding. This model can account for the selectivity of the vasopressin-stimulated urea transport, its inhibition by urea and thiourea analogues, the facilitated transport of urea, inhibition of tracer urea flux from either the cis or the trans position, and finally the preservation of the urea transport machinery following glutaraldehyde fixation.

scholarly journals Reflection coefficients of homopore membranes: effect of molecular size and configuration.

1979 ◽  
Vol 73 (1) ◽  
pp. 49-60 ◽  
Author(s):  
J S Schultz ◽  
R Valentine ◽  
C Y Choi
Keyword(s):  
Hydrostatic Pressure ◽  
Pore Size ◽  
Osmotic Pressure ◽  
Water Flow ◽  
Molecular Size ◽  
Reflection Coefficients ◽  
Osmotic Water ◽  
Molecular Rigidity ◽  
Flow Through ◽  
Osmotic Water Flow

Osmotic water flow through membranes with uniform defined pores was measured for a variety of macromolecular solutes. Water flow increased linearly with applied hydrostatic pressure, allowing the effective osmotic pressure of the solutes to be estimated by extrapolation. Reflection coefficients for each solute-membrane combination were calculated and correlated with the ratio of solute size to pore size. For the same mean molecular size, proteins were found to have larger reflection coefficients than dextrans. Molecular rigidity may play a role in this difference in behavior.

Polyclonal antibodies in study of ADH-induced water channels in frog urinary bladder

1991 ◽  
Vol 261 (3) ◽  
pp. F437-F442
Author(s):  
G. Valenti ◽  
G. Calamita ◽  
M. Svelto
Keyword(s):  
Urinary Bladder ◽  
Water Flow ◽  
Apical Membrane ◽  
Polyclonal Antibodies ◽  
Immune Serum ◽  
Frog Urinary Bladder ◽  
Hormonal Stimulation ◽  
Osmotic Water ◽  
Triton X ◽  
Osmotic Water Flow

It is now generally accepted that changes in water permeability in anti-diuretic hormone (ADH)-responsive target epithelial cells result from the insertion in the plasma apical membrane of new components that contain channels for water. The specificity of these channels suggests that they are formed by intrinsic proteins having access to both facies and spanning the whole membrane. We have previously shown that Triton X-100 apical extracts from ADH-stimulated frog urinary bladder contain some proteins inserted under hormonal stimulation. In the present study we have developed polyclonal antibodies using Triton X-100 extract as an immunogen. After considering the inhibitory effect exerted by the whole immune serum on the osmotic water flow, we used different adsorption steps to select, from the immune serum, antibodies to apical membrane proteins inserted in response to the hormone. Immunoblot analysis of these selected antibodies shows that they recognize seven to eight proteins, of which 55-, 35-, 26-, and 17-kDa proteins are always present. Antibodies to these four proteins, affinity purified on nitrocellulose sheets, inhibited ADH-induced osmotic water flow. Altogether these results strongly suggest that proteins of 55, 35, 26, and 17 kDa (or at least one of them) are likely to be involved in the mechanism of water transport.

scholarly journals A model of electrodiffusion and osmotic water flow and its energetic structure

2011 ◽  
Vol 240 (22) ◽  
pp. 1835-1852 ◽  
Author(s):  
Yoichiro Mori ◽  
Chun Liu ◽  
Robert S. Eisenberg
Keyword(s):  
Water Flow ◽  
Osmotic Water ◽  
Osmotic Water Flow

Ultrastructural changes in isolated perfused proximal tubules during osmotic water flow

1987 ◽  
Vol 253 (6) ◽  
pp. F1091-F1104
Author(s):  
A. B. Maunsbach ◽  
S. Tripathi ◽  
E. L. Boulpaep
Keyword(s):  
Cell Volume ◽  
Water Flow ◽  
Streaming Potential ◽  
Volume Density ◽  
Proximal Tubules ◽  
Ultrastructural Changes ◽  
Organic Substrates ◽  
Osmotic Water ◽  
Cell Volumes ◽  
Osmotic Water Flow

Steady-state effects of osmotic gradients on extracellular spaces and cell volumes were studied by ultrastructural morphometry in isolated perfused Ambystoma proximal tubules. Solute clamping, high-resolution pressure and flow control of lumen and bath solutions were all ascertained before and during fixation. Isosmotic removal of organic substrates in the lumen reversibly abolished transport, as confirmed by transepithelial potential decrease from -4.7 +/- 0.5 to -0.5 +/- 0.2 mV (n = 8) but had no effect on ultrastructural parameters. The walls of the extracellular spaces are therefore not deformed by spontaneous solute-coupled water transport. A hyperosmolar lumen generated a streaming potential of -1.56 +/- 0.15 mV (n = 8), reduced cell volume to 65%, reduced lateral intercellular space (LIS) volume to 20%, and LIS volume density to 29% of control without significant effects on the volume of the basal extracellular labyrinth (BEL). A hyperosmolar bath generated a streaming potential of +1.96 +/- 0.30 mV (n = 7), reduced cell volume to 68%, and increased LIS volume density to 236% of control. BEL volume was 55% larger during lumen-to-bath flow than during bath-to-lumen flow. Because cell volume reduction is very similar for both directions of osmotic water flow, the oppositely directed volume changes in the extracellular spaces are secondary to transepithelial water flow. The greater change in volume of LIS compared with BEL indicates that the outermost parts of the LIS are more resistive to transepithelial water flow than the slitlike communications of the BEL with the peritubular space.

Evidence for transcellular osmotic water flow in rat proximal tubules

1985 ◽  
Vol 249 (1) ◽  
pp. F124-F131 ◽  
Author(s):  
P. A. Preisig ◽  
C. A. Berry
Keyword(s):  
Surface Area ◽  
Water Flow ◽  
Water Permeability ◽  
Channel Length ◽  
Osmotic Gradient ◽  
Osmotic Water Permeability ◽  
Osmotic Water ◽  
Major Route ◽  
Osmotic Water Flow

To determine the predominant pathway for transepithelial osmotic water flow, the transepithelial osmotic water permeability [Pf(TE)] and the apparent dimensions of paracellular pores and slits were determined in rat proximal convoluted tubules microperfused in vivo. To measure Pf(TE), tubules were perfused with a hyposmotic, cyanide-containing solution. Pf(TE), calculated from the observed volume flux in response to the measured log mean osmotic gradient, was 0.12-0.15 cm/s, assuming sigmaNaCl equal to 1.0-0.7, respectively. The dimensions of the paracellular pathways were determined using measured sucrose and mannitol permeabilities (nonelectrolytes confined to the extracellular space). These were 0.43 and 0.87 X 10(-5) cm/s, respectively. By using the ratio of these permeabilities, their respective free solution diffusion coefficients and molecular radii, and the Renkin equation, the radius of the nonelectrolyte-permeable pores and the total pore area/cm2 surface area/channel length were calculated to be 1.4 nm and 3.56 cm-1, respectively. Similar calculations for slits yielded a slit half-width of 0.8 nm and a total slit area/cm2 surface area/channel length of 3.16 cm-1. The osmotic water permeability of these nonelectrolyte-permeable pathways was calculated by Poiseuille's law to be 0.0018 cm/s (pores) or 0.0014 cm/s (slits), at most 2% of Pf(TE). We conclude that the nonelectrolyte-permeable pathway in the tight junctions is not the major route of transepithelial osmotic water flow in the rat proximal tubule.

scholarly journals THE EFFECT OF SMOOTH MUSCLE ON THE INTERCELLULAR SPACES IN TOAD URINARY BLADDER

1970 ◽  
Vol 46 (2) ◽  
pp. 235-244 ◽  
Author(s):  
Donald R. DiBona ◽  
Mortimer M. Civan
Keyword(s):  
Smooth Muscle ◽  
Urinary Bladder ◽  
Water Flow ◽  
Toad Urinary Bladder ◽  
Reliable Index ◽  
Intercellular Spaces ◽  
Phase Microscopy ◽  
Osmotic Water ◽  
Smooth Muscle Relaxant ◽  
Osmotic Water Flow

Phase microscopy of toad urinary bladder has demonstrated that vasopressin can cause an enlargement of the epithelial intercellular spaces under conditions of no net transfer of water or sodium. The suggestion that this phenomenon is linked to the hormone's action as a smooth muscle relaxant has been tested and verified with the use of other agents effecting smooth muscle: atropine and adenine compounds (relaxants), K+ and acetylcholine (contractants). Furthermore, it was possible to reduce the size and number of intercellular spaces, relative to a control, while increasing the rate of osmotic water flow. A method for quantifying these results has been developed and shows that they are, indeed, significant. It is concluded, therefore, that the configuration of intercellular spaces is not a reliable index of water flow across this epithelium and that such a morphologic-physiologic relationship is tenuous in any epithelium supported by a submucosa rich in smooth muscle.

Evidence for the role of the Ns protein in the forskolin actions on osmotic water flow

1988 ◽  
Vol 90 (4) ◽  
pp. 825
Author(s):  
V Casavola ◽  
G Valenti ◽  
G Calamita ◽  
J Bourguet ◽  
M Svelto
Keyword(s):  
Water Flow ◽  
Osmotic Water ◽  
Osmotic Water Flow
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