August Krogh Lecture. The renal concentrating mechanism in insects and mammals: a new hypothesis involving hydrostatic pressures

1995 ◽  
Vol 268 (5) ◽  
pp. R1087-R1100 ◽  
Author(s):  
B. Schmidt-Nielsen
Keyword(s):  
Hydrostatic Pressure ◽  
Water Potential ◽  
Plasma Membranes ◽  
Water Molecules ◽  
Osmotic Concentration ◽  
Pelvic Wall ◽  
Collecting Ducts ◽  
Renal Concentrating Mechanism ◽  
Peristaltic Contractions ◽  
New Hypothesis

Water moves from compartments of higher to compartments of lower water potential. Osmotically active solutes and negative hydrostatic pressure both lower water potential by stretching the hydrogen bonds between water molecules (Hammel-Scholander hypothesis). In trees the negative hydrostatic pressure in the sap is balanced by the osmotic pressure of the leaves. In response to differences in water potential, water flows across biological membranes through water-filled pores. Protein molecules, aquaporins, forming hourglass-shaped pores have been identified, cloned, and located in plasma membranes in mammalian as well as other tissues. Water molecules flow single file through aquaporins. Insects concentrate the urine in the rectum. Mammals concentrate the urine in the collecting ducts in the inner medulla. In both, a compartment with a high osmotic concentration is created through ion transport. Both have a muscular coat surrounding the tissue, which shows peristaltic contractions. In insects it is the muscular layer around the rectum; in mammals it is the renal pelvic wall that surrounds the papilla. Mechanisms are proposed whereby these peristaltic contractions, through the creation of positive and negative hydrostatic pressures in the tissues, can lead to hyperosmotic excreta.

Interdependence of urea and electrolytes in production of a concentrated urine

1961 ◽  
Vol 200 (6) ◽  
pp. 1125-1132 ◽  
Author(s):  
Bodil Schmidt-Nielsen ◽  
Roberta O'Dell ◽  
Humio Osaki
Keyword(s):  
Water Deprivation ◽  
Inverse Relationship ◽  
Electrolyte Concentration ◽  
Urea Concentration ◽  
Osmotic Concentration ◽  
Salt Loading ◽  
Collecting Ducts ◽  
Desert Rodent ◽  
Concentrate Urea

In most mammals, ability to concentrate urea in the urine exceeds that for electrolytes; this was not found in beaver, pig, and the desert rodent Psammomys. When these animals were exposed to water deprivation, Pitressin administration, urea, and salt loading, the urine osmotic concentration was constant regardless of which solute dominated in the urine. When the urea concentration was high, total electrolyte concentration was low, and vice versa. In salt-loaded animals, urea and electrolyte concentrations in the papilla nearly equaled urea and total electrolyte concentrations in the urine. In urea-loaded animals, urea concentration in the papilla was markedly lower than in urine and electrolyte concentration was correspondingly higher, so that calculated osmolarity in the tissue still equaled the osmolarity in the urine. It is possible that the permeability of the collecting ducts to urea changes with the loading solute. This could explain the inverse relationship between the urea and electrolyte concentrations in the urine.

Lectin-gold labeling of glycoconjugates in normal and Brattleboro rat papilla: effect of vasopressin

1988 ◽  
Vol 254 (3) ◽  
pp. C450-C458 ◽  
Author(s):  
P. Weyer ◽  
D. Brown ◽  
L. Orci
Keyword(s):  
Epithelial Cell ◽  
Plasma Membranes ◽  
Collecting Duct ◽  
Helix Pomatia ◽  
Major Effect ◽  
Urinary Concentration ◽  
Brattleboro Rats ◽  
Cell Plasma ◽  
Collecting Ducts ◽  
Helix Pomatia Lectin

Some reports suggest that the plasma membrane glycocalyx of collecting duct epithelial cells, as well as interstitial glycoconjugates, may be involved in vasopressin action and urinary concentration. In view of this, we have used the lectin-gold technique to map and quantify Helix pomatia lectin (HPL)-binding sites in the inner medulla of kidneys from normal Long-Evans rats, vasopressin-deficient Brattleboro rats, and Brattleboro rats treated for up to 5 wk with exogenous vasopressin. The results show that the labeling of epithelial cell plasma membranes from collecting ducts and thin limbs of Henle is not different between normal and Brattleboro rats, and the labeling is not modified by chronic vasopressin treatment. In contrast, the heavy interstitial labeling seen in normal rats is virtually absent from Brattleboro rats, but it is progressively restored by chronic vasopressin treatment of Brattleboro rats. These results show that vasopressin does not modify HPL-binding glycoconjugates on epithelial cell plasma membranes, but that vasopressin treatment has a major effect on HPL-binding glycoconjugates in the medullary interstitium.

Lectin-gold cytochemistry reveals intercalated cell heterogeneity along rat kidney collecting ducts

1985 ◽  
Vol 248 (3) ◽  
pp. C348-C356 ◽  
Author(s):  
D. Brown ◽  
J. Roth ◽  
L. Orci
Keyword(s):  
Plasma Membranes ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Lectin Binding ◽  
Helix Pomatia ◽  
Intercalated Cells ◽  
Double Labeling ◽  
Thin Sections ◽  
Intercalated Cell ◽  
Collecting Ducts

The lectin-gold technique was used to detect Helix pomatia and Dolichos biflorus lectin binding sites directly on semithin and thin sections of rat kidney collecting ducts. Intercalated cell apical plasma membranes and the membranes of apical cytoplasmic vesicles were heavily labeled in the cortex and outer stripe of the outer medulla but were negative or very weakly labeled in the inner stripe and inner medulla. In contrast, clear cell apical membranes were labeled along the entire length of the collecting duct. Double labeling of semithin cryostat sections with a specific antibody and lectin-gold complexes was used to demonstrate that the intercalated cells in all regions studied contained carbonic anhydrase, even though the lectin binding differed. These results indicate that, in terms of their glycocalyx composition, intercalated cells represent a heterogeneous population in different regions of the collecting duct.

scholarly journals Behavior of plant plasma membranes under hydrostatic pressure as monitored by fluorescent environment-sensitive probes

2010 ◽  
Vol 1798 (8) ◽  
pp. 1601-1607 ◽  
Author(s):  
Yann Roche ◽  
Andrey S. Klymchenko ◽  
Patricia Gerbeau-Pissot ◽  
Patrick Gervais ◽  
Yves Mély ◽  
...  
Keyword(s):  
Hydrostatic Pressure ◽  
Plasma Membranes

Effects of Ion-Water Potentials in Molecular Dynamics Simulation of Ion Distribution in Nanochannels

2006 ◽  
Author(s):  
Dongyan Xu ◽  
Deyu Li ◽  
Yongsheng Leng ◽  
Yunfei Chen
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Water Potential ◽  
Ion Concentration ◽  
Dynamics Simulation ◽  
Water Molecules ◽  
Surface Charges ◽  
Ion Distribution ◽  
Hydrogen Atoms ◽  
Interaction Potentials

Understanding ion and fluid transport through highly confined nanochannels is important for the study of many interesting phenomena in nature and for the design of novel nanofluidic devices. Molecular dynamics has been proved to be a powerful tool to investigate the transport of ion and fluid in nanochannels, however, the results of molecular dynamics simulation depend on the selection of intermolecular potentials in the simulation. In this work, we applied two different ionwater interaction potentials to study their effects in the molecular dynamics simulation of ion distribution in the nanochannels between two parallel charged surfaces. Water was simulated with the TIP4P and SPC/E models and the electrostatic interaction between ions, water molecules, and surface charges was modeled by using Ewald summation algorithm with the slab correction. Two different interaction potentials between the ion and water molecules, one based on simple Lennard-Jones potential and the other based on the Bounds' ion-water potential, were adopted to explore the effects of ion-water interactions on the ion distribution in nanochannels. The Bounds' model takes into account the interactions between ions and both oxygen and hydrogen atoms in the water molecules. Ion concentration profiles in nanochannels with these two different potentials were calculated and results showed that the ion-water interaction potential could significantly affect the ion distribution in nanochannels. We expect that the ion-water potential could also have important effect on modeling of electroosmotic flow through nanochannels.

scholarly journals Transport Characteristics of Plasma Membranes of PK-15 Passaged Cells

2021 ◽  
Vol 31 (1) ◽  
pp. 14-22
Author(s):  
Larisa Kuleshova ◽  
◽  
Igor Kovalenko ◽  
Svetlana Kovalenko ◽  
Tetiana Tsibulko ◽  
...  
Keyword(s):  
Experimental Data ◽  
Plasma Membranes ◽  
Volume Ratio ◽  
Relative Volume ◽  
Water Molecules ◽  
Analytical Evaluation ◽  
Passive Transport ◽  
Cell Parameters ◽  
Permeability Coefficients ◽  
Optimal Duration

The values of permeability coefficients to water molecules and cryoprotectants are demanded to select the optimal duration of exposure of cells in cryoprotective media at the stage of their preparation for cryopreservation, as well as to find optimal cooling and warming rates during the freeze-thawing of cell suspensions. The necessary numerical values of such cell parameters as the osmotically inactive volume α and the surface-area-to-volume ratio γ were obtained for the analytical evaluation of the permeability coefficients of the PK-15 cells’ plasma membranes using physico-mathematical modelling. The permeability coefficients kp of the plasma membranes of PK-15 cells to 1,2-PD, EG, DMSO and glycerol cryoprotectants molecules, as well as the filtration coefficients Lp to water molecules at temperatures of 25, 15 and 5°C were determined by approximating the experimental data of the change in relative volume of cells on exposure time in the studied solutions by theoretical curves calculated on the basis of physical and mathematical model of passive transport of water and permeable substances under the condition of their maximum coincidence. The value of the activation energy of the transmembrane transfer of molecules of these substances is calculated

The i-TTM model for ab initio-based ion–water interaction potentials. II. Alkali metal ion–water potential energy functions

2016 ◽  
Vol 18 (44) ◽  
pp. 30334-30343 ◽  
Author(s):  
Marc Riera ◽  
Andreas W. Götz ◽  
Francesco Paesani
Keyword(s):  
Alkali Metal ◽  
Potential Energy ◽  
Ab Initio ◽  
Water Potential ◽  
Metal Ion ◽  
Alkali Metal Ions ◽  
Water Molecules ◽  
Energy Functions ◽  
Potential Energy Functions ◽  
Water Interaction

A new set of i-TTM potential energy functions describing the interactions between alkali metal ions and water molecules is reported.

Localization of ral, a small Mr GTP-binding protein, to collecting duct cells in bovine and rat kidney

1991 ◽  
Vol 261 (6) ◽  
pp. F1063-F1070
Author(s):  
A. Gupta ◽  
B. Bastani ◽  
P. Chardin ◽  
K. A. Hruska
Keyword(s):  
Gene Product ◽  
Plasma Membranes ◽  
Binding Protein ◽  
Collecting Duct ◽  
Rat Kidney ◽  
Kidney Cortex ◽  
Gtp Binding Protein ◽  
Bovine Kidney ◽  
Gtp Binding ◽  
Collecting Ducts

Plasma membranes from bovine kidney cortex were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and transferred to nitrocellulose membranes. Blotting with [alpha-32P]GTP and [35S]GTP gamma S demonstrated specific binding to three and six distinct protein bands, respectively, in the 20,000- to 29,000-Mr range. This indicated the presence of small Mr GTP binding proteins (smg) in bovine kidney cortex. Only one smg with 28,000 Mr was labeled with hydrolysis-resistant GTP photoaffinity probe p3-(4-azidoanilido)-p1-5GTP (AAGTP). The major smg in platelet membranes that binds GTP on nitrocellulose blots has been identified as ral-Mr 29,000. With the use of an antiserum against the ral A gene product, one of the smg with Mr of 29,000 present in bovine renal cortical plasma membranes was identified as ral. Ral was absent from glomerular homogenate, suggesting that it is localized to the tubular segments of the nephron. Ral was detected only in the particulate fraction and not the cytosol. Further subcellular localization of ral was investigated by immunohistochemical staining. Anti-ral antibody immunostained the apical and basolateral membranes of cells in the cortical and medullary collecting ducts in a speckled pattern in the bovine kidney. In the rat kidney, however, uniform linear staining of cortical and medullary collecting ducts predominantly localized to the apical membrane was observed. To date, no function has been assigned to ral. Localization of the ral gene product to the collecting duct suggests a specific functional role for this GTP-binding protein.

scholarly journals The Osmotic Mechanism of the Cuttlebone

1961 ◽  
Vol 41 (2) ◽  
pp. 351-363 ◽  
Author(s):  
E. J. Denton ◽  
J. B. Gilpin-Brown ◽  
J. V. Howarth
Keyword(s):  
Hydrostatic Pressure ◽  
Shallow Water ◽  
Sea Water ◽  
Ionic Concentration ◽  
Chloride Ions ◽  
Osmotic Concentration ◽  
Narrow Channels ◽  
Gas Space

Experiments are described which test the hypothesis that the cuttlefish controls the relative volumes of gas space and liquid within its cuttlebone by an osmotic mechanism acting across the siphuncular surface of the bone. When the animal is at the bottom of the sea it would maintain the gas space within the cuttlebone by balancing the hydrostatic pressure of the sea by an osmotic force between the liquid within the cuttlebone and the blood.In cuttlefish kept for some weeks in shallow water in an aquarium all the liquid taken from the cuttlebone is almost isotonic with the animals’ blood.In animals recently hauled from the bottom of the sea the cuttlebone liquid is markedly hypotonic to sea water and hence to the blood.These lower osmotic concentrations are given chiefly by reduction in the concentrations of the sodium and chloride ions.After bringing animals up from about 70 m to the surface of the sea the osmotic concentration of the cuttlebone liquid rises from about 75% of sea water some 40 min after starting to haul the trawl, to about 97% of sea water 6 h later. Extrapolation back to the time at which hauling began gives a concentration of salts close to that predicted by the osmotic hypothesis.Whilst the cuttlebone liquid is increasing in ionic concentration the liquid deeper in the cuttlebone is hypotonic to that just inside the siphuncular surface. This is explained in terms of the slowness of exchange of salts along the narrow channels between the lamellae of the cuttlebone.

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