Electrophysiology of salamander proximal tubule. II. Interspace NaCl concentrations and solute-coupled water transport

1986 ◽  
Vol 251 (2) ◽  
pp. F334-F347
Author(s):  
H. Sackin
Keyword(s):  
Low Temperature ◽  
Proximal Tubule ◽  
Water Transport ◽  
Time Course ◽  
Fluid Transport ◽  
Bath Temperature ◽  
Null Point ◽  
Constant Composition ◽  
Nacl Concentration ◽  
Test Concentration

The role of the paracellular interspace in solute-coupled water transport was investigated in isolated perfused salamander (Ambystoma) proximal tubules using a null-point technique to estimate interspace NaCl concentrations. Constant composition of luminal fluid was maintained by rapid (200 nl/min) perfusion of tubules 600,micron or less in length. Inhibition of active transport by a decrease in bath temperature from 22 to 0 degrees C in 400 ms produced rapid depolarizations of both the transepithelial (Vte) and basolateral (Vbl) potential, followed by slower changes in potential that occurred at low temperature. During this period, the time course of Vbl was independent of small changes in bath NaCl concentration, whereas the time course of Vte at low temperature varied from a slow depolarization to a slow repolarization depending on whether the concentration of NaCl in the bath equaled or exceeded that in the perfusate. Absence of a slow change in Vte at low temperature indicated a match between the NaCl concentration of the interspace and the test concentration of NaCl in the bath. Using this technique with 12 tubules, the normal interspace NaCl concentration appeared to be approximately 4% above the NaCl concentration of either the lumen or bath, demonstrating that the interspace of the salamander proximal tubule can function as a local hyperosmotic compartment to facilitate fluid transport between solutions of identical composition.

Electrophysiology of salamander proximal tubule. I. Effects of rapid cooling

1986 ◽  
Vol 251 (2) ◽  
pp. F319-F333
Author(s):  
H. Sackin
Keyword(s):  
Membrane Potential ◽  
Low Temperature ◽  
Proximal Tubule ◽  
Basolateral Membrane ◽  
Bath Temperature ◽  
Ambystoma Tigrinum ◽  
Ionic Selectivity ◽  
Anion Selectivity ◽  
Nacl Concentration ◽  
Basolateral Membrane Potential

The response of the amphibian proximal tubule to a rapid decrease in temperature was studied in isolated perfused tubules of Ambystoma tigrinum. Cooling from 23 to 4 degrees C increased paracellular and cellular electrical resistances by factors of 1.7 and 3.6, respectively, but had virtually no effect on the ionic selectivity of the paracellular pathway. When lumen and bath solutions were maintained identical by rapid tubule perfusion, decreasing bath temperature from 22 to 0 degree C in 400 ms depolarized the transepithelial potential (Vte) from -3.7 +/- 0.3 to -1.1 +/- 0.2 mV and depolarized the basolateral membrane potential (Vbl) from -52 +/- 3 to -45 +/- 3 mV (n = 12). These fast depolarizations were followed by slower depolarizations of both Vte and Vbl that continued throughout the period of low temperature. Only approximately 30% of the initial slow depolarization of Vte at low temperature could be explained by changes in electrical resistance and cell membrane potential. The remaining 70% of this Vte depolarization at low temperature is consistent with equilibration of a hypertonic interspace with isotonic lumen and bath solutions. Given the anion selectivity of Ambystoma proximal tubule, the magnitude of this slow Vte depolarization implies an interspace NaCl concentration 2-5% higher than the NaCl concentration in either the lumen or bath solutions.

Dependence of ion fluxes on fluid transport by rat proximal tubule

1986 ◽  
Vol 250 (4) ◽  
pp. F680-F689 ◽  
Author(s):  
K. Bomsztyk ◽  
F. S. Wright
Keyword(s):  
Proximal Tubule ◽  
Fluid Transport ◽  
Rat Kidney ◽  
Water Flux ◽  
Fluid Secretion ◽  
Proximal Convoluted Tubule ◽  
Ion Fluxes ◽  
Fluid Absorption ◽  
Fluid Flux ◽  
K Transport

The effects of changes in transepithelial water flux (Jv) on sodium, chloride, calcium, and potassium transport by the proximal convoluted tubule were examined by applying a microperfusion technique to surface segments in kidneys of anesthetized rats. Perfusion solutions were prepared with ion concentrations similar to those in fluid normally present in the later parts of the proximal tubule. Osmolality of the perfusate was adjusted with mannitol. With no mannitol in the perfusates, net fluid absorption was observed. Addition of increasing amounts of mannitol first reduced Jv to zero and then reversed net fluid flux. At the maximal rates of fluid absorption, net absorption of Na, Cl, Ca, and K was observed. When Jv was reduced to zero, Na, Cl, and Ca absorption were reduced and K entered the lumen. Na, Cl, and Ca secretion occurred in association with the highest rates of net fluid secretion. The lumen-positive transepithelial potential progressively increased as the net fluid flux was reduced to zero and then reversed. The results demonstrate that changes in net water flux can affect Na, Cl, Ca, and K transport by the proximal convoluted tubule of the rat kidney. These changes in net ion fluxes are not entirely accounted for by changes in bulk-phase transepithelial electrochemical gradients.

EARLYWOOD VESSELS IN RING-POROUS TREES BECOME FUNCTIONAL FOR WATER TRANSPORT AFTER BUD BURST AND BEFORE THE MATURATION OF THE CURRENT-YEAR LEAVES

IAWA Journal ◽  
2016 ◽  
Vol 37 (2) ◽  
pp. 315-331 ◽  
Author(s):  
Peter Kitin ◽  
Ryo Funada
Keyword(s):  
Water Transport ◽  
Time Course ◽  
Growing Season ◽  
Early Spring ◽  
Vessel Element ◽  
Full Time ◽  
Bud Burst ◽  
Long Time ◽  
Wall Perforation ◽  
Earlywood Vessels

This paper reviews the development of xylem vessels in ring-porous dicots and the corresponding leaf phenology. Also included are our original observations on the time-course of vessel element growth, secondary wall deposition, and end wall perforation in the deciduous hardwood Kalopanax septemlobus. Different patterns of xylem growth and phenology serve different strategies of the species for adaptation to seasonal climates. Trees with ring-porous xylem form wide earlywood vessels (EWV) in spring and narrow latewood vessels in summer. The wide EWV become embolized or blocked with tyloses by the end of the growing season while the narrow vessels may remain functional for many years. The co-occurrence of wide and narrow vessels provides both efficiency and safety of the water transport as well as a potentially longer growing season. It has for a long time been assumed that EWV in ring-porous hardwoods are formed in early spring before bud burst in order to supply sap to growing leaves and shoots.However, the full time-course of development of EWV elements from initiation of growth until maturation for water transport has not been adequately studied until recently. Our observations clarify a crucial relationship between leaf maturation and the maturation of earlywood vessels for sap transport. Accumulated new evidence shows that EWV in branches and upper stem parts develop earlier than EWV lower in the stem. The first EWV elements are fully expanded with differentiated secondary walls by the time of bud burst. In lower stem parts, perforations in vessel end walls are formed after bud burst and before the new leaves have achieved full size. Therefore, the current-year EWV network becomes functional for water transport only by the time when the first new leaves are mature.

Stimulation of phosphate transport in the proximal tubule by metabolic substrates

1984 ◽  
Vol 247 (4) ◽  
pp. F582-F587 ◽  
Author(s):  
S. R. Gullans ◽  
P. C. Brazy ◽  
L. J. Mandel ◽  
V. W. Dennis
Keyword(s):  
Proximal Tubule ◽  
Fluid Transport ◽  
Initial Rate ◽  
Tricarboxylic Acid Cycle ◽  
Phosphate Transport ◽  
Glucose Absorption ◽  
Metabolic Substrates ◽  
Tricarboxylic Acid Cycle Intermediates ◽  
Stimulation Of

Studies of phosphate transport in the proximal tubule have recently focused on interactions with cellular metabolism. The present studies demonstrate that two fatty acids, valerate and butyrate, and two tricarboxylic acid cycle intermediates, succinate and malate, stimulate net phosphate transport in the rabbit proximal tubule by 34-117%. Valerate had no effect on the total uptake of inorganic [32P]phosphate into suspensions of proximal tubules but did enhance the initial rate of influx. Net fluid transport was unaffected by these substrates although glucose absorption increased by 10-15% following the addition of either valerate or succinate. Since valerate, butyrate, and succinate are known to stimulate gluconeogenesis and respiration, we evaluated the role of gluconeogenesis in the stimulation of phosphate transport. The addition of 3-mercaptopicolinate (1 mM), an inhibitor of gluconeogenesis, did not alter phosphate transport, nor did it prevent the valerate-induced stimulation of phosphate transport. We conclude that valerate, butyrate, succinate, and malate enhance phosphate transport by the proximal convoluted tubule. This action appears to be unrelated to effects on gluconeogenesis and may be related to close links between phosphate transport and oxidative metabolism.

FRACTAL MODELS FOR GAS–WATER TRANSPORT IN SHALE POROUS MEDIA CONSIDERING WETTING CHARACTERISTICS

Fractals ◽  
2020 ◽  
Vol 28 (07) ◽  
pp. 2050138
Author(s):  
QI ZHANG ◽  
XINYUE WU ◽  
QINGBANG MENG ◽  
YAN WANG ◽  
JIANCHAO CAI
Keyword(s):  
Fractal Dimension ◽  
Pore Structure ◽  
Pore Pressure ◽  
Surface Diffusion ◽  
Water Transport ◽  
Relative Permeability ◽  
Fluid Transport ◽  
Water Saturation ◽  
Fractal Theory ◽  
Gas Slippage

Complicated gas–water transport behaviors in nanoporous shale media are known to be influenced by multiple transport mechanisms and pore structure characteristics. More accurate characterization of the fluid transport in shale reservoirs is essential to macroscale modeling for production prediction. This paper develops the analytical relative permeability models for gas–water two-phase in both organic and inorganic matter (OM and IM) of nanoporous shale using the fractal theory. Heterogeneous pore size distribution (PSD) of the shale media is considered instead of the tortuous capillaries with uniform diameters. The gas–water transport models for OM and IM are established, incorporating gas slippage described by second-order slip condition, water film thickness in IM, surface diffusion in OM, and the total organic carbon. Then, the presented model is validated by experimental results. After that, sensitivity analysis of gas–water transport behaviors based on pore structure properties of the shale sample is conducted, and the influence factors of fluid transport behaviors are discussed. The results show that the gas relative permeability is larger than 1 at the low pore pressure and water saturation. The larger pore pressure causes slight effect of gas slippage and surface diffusion on the gas relative permeability. The larger PSD fractal dimension of IM results in larger gas relative permeability and smaller water relative permeability. Besides, the large tortuosity fractal dimension will decrease the gas flux at the same water saturation, and the surface diffusion decreases with the increase of tortuosity fractal dimension of OM and pore pressure. The proposed models can provide an approach for macroscale modeling of the development of shale gas reservoirs.

scholarly journals Nanostructure of serpentinisation products: Importance for water transport and low-temperature alteration

2021 ◽  
Vol 576 ◽  
pp. 117212
Author(s):  
Benjamin Malvoisin ◽  
Anne-Line Auzende ◽  
Peter B. Kelemen
Keyword(s):  
Low Temperature ◽  
Water Transport

A Calcium-Dependent Mechanism Responsible for Increasing the Freezing Tolerance of the Bivalve Mollusc Modiolus Demissus

1977 ◽  
Vol 69 (1) ◽  
pp. 13-21
Author(s):  
DENNIS J. MURPHY
Keyword(s):  
Low Temperature ◽  
Freezing Tolerance ◽  
Time Course ◽  
Cell Membranes ◽  
Contractile Response ◽  
Temperature Acclimation ◽  
Freezing Injury ◽  
Total Change ◽  
Calcium Dependent ◽  
Dependent Mechanism

1. A time course of the changes in blood Ca2+ and freezing tolerance of Modiolus demissus (Dillwyn) demonstrated that increases in freezing tolerance parallel increases in blood Ca2+. The increases in freezing tolerance occurred rapidly, suggesting that Ca2+ affects freezing tolerance directly by its presence in the blood. 2. The presence of La3+ reduced the freezing tolerance of isolated foot muscle. Thus, Ca2+ appears to increase freezing tolerance directly by binding to cell membranes. 3. The loss of the contractile response of freeze-thawed foot muscle to Ach, KCl and caffeine and the continued response to CaCl2 suggested that cell membranes are the primary sites of freezing injury. 4. The increase in blood Ca2+ following low-temperature acclimation accounted for only 40% of the total change in freezing tolerance. Therefore, other mechanisms responsible for increasing the freezing tolerance of M. demissus following low temperature acclimation also exist.

Increased fluid absorption and cell volume in isolated rabbit proximal straight tubules after in vivo DOCA administration

1981 ◽  
Vol 241 (5) ◽  
pp. F502-F508 ◽  
Author(s):  
M. A. Knepper ◽  
M. B. Burg
Keyword(s):  
Proximal Tubule ◽  
Cell Volume ◽  
Fluid Transport ◽  
Sodium Intake ◽  
Plasma Concentrations ◽  
Dietary Sodium ◽  
Fluid Absorption ◽  
Direct Stimulation ◽  
Stimulation Of

To investigate whether mineralocorticoids affect the intrinsic capacity of the proximal tubule to absorb sodium and fluid, rabbits were chronically treated a number of ways to systematically vary plasma concentrations of mineralocorticoid hormones. The rate of fluid absorption and tubule dimensions were measured in superficial S2 segments from these rabbits. Chronic administration of deoxycorticosterone acetate (DOCA) was associated with a 67% increase in fluid absorption and a 29% increase in cell volume per unit tubule length. However, neither adrenalectomy nor low sodium diet significantly affected either fluid absorption or cell volume. Furthermore, marked dietary sodium restriction prevented the response to DOCA. We conclude that the DOCA-induced increases in fluid absorption and cell volume do not result from a direct stimulation of the proximal tubular cells by the steroid but more likely are responses to systemic effects of DOCA administration that are dependent on the level of sodium intake. Thus, we find no evidence for a direct mineralocorticoid stimulation of sodium and fluid transport by the S2 portion of the proximal tubule.

Water permeability and pathways in the proximal tubule

1983 ◽  
Vol 245 (3) ◽  
pp. F279-F294 ◽  
Author(s):  
C. A. Berry
Keyword(s):  
Proximal Tubule ◽  
Water Transport ◽  
Water Permeability ◽  
Intercellular Space ◽  
Proximal Convoluted Tubule ◽  
Pressure Gradients ◽  
Solvent Drag ◽  
Lateral Intercellular Space ◽  
Volume Absorption ◽  
Osmotic Water

The route of water transport in the proximal tubule could be either transjunctional or transcellular. A transjunctional route is supported by data showing high osmotic-to-diffusive water permeability ratios, the possible correlation of junctional leakiness to ions and nonelectrolytes with water permeability, and solvent drag of nonelectrolytes and ions. These data, however, are not convincing. A transcellular route of water transport is supported by data showing that the osmotic water permeability (Pf) for apical and/or basolateral cell membranes is sufficiently high to account for the transepithelial Pf, making a tentative conclusion for a transcellular route of water transport possible. In addition, measurements of Pf have yielded insights into the mechanism of solute-solvent coupling. Pf has been reported to be mostly between 0.1 and 0.3 cm/s. In the rabbit proximal straight and the Necturus proximal convoluted tubule, in which water transport rates are low, this range of Pf will account for volume absorption with only small osmotic gradients (less than 6 mosmol). Higher osmotic gradients are required in the rat and possibly the rabbit proximal convoluted tubule, where water transport rates are higher. Solute-solvent coupling in all species is probably due to both luminal hypotonicity and lateral intercellular space hypertonicity. These two processes are directly linked. Mass balance requires that generation of luminal hypotonicity also generates a hypertonic absorbate and, thus, some degree of lateral intercellular space hypertonicity. It is likely that, in the rabbit at least, effective osmotic pressure gradients due to differences in solute reflection coefficients play little role in solute-solvent coupling.

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