scholarly journals Influence of serum proteins on net fluid reabsorption of isolated proximal tubules

1972 ◽  
Vol 2 (2) ◽  
pp. 66-75 ◽  
Author(s):  
Jared J. Grantham ◽  
Patti B. Qualizza ◽  
Larry W. Welling
Keyword(s):  
Serum Proteins ◽  
Proximal Tubules ◽  
Fluid Reabsorption

Return of the secretory kidney

2002 ◽  
Vol 282 (1) ◽  
pp. F1-F9 ◽  
Author(s):  
Jared J. Grantham ◽  
Darren P. Wallace
Keyword(s):  
Glomerular Filtration ◽  
Extracellular Fluid ◽  
Fluid Secretion ◽  
Proximal Tubules ◽  
Renal Tubules ◽  
Functional Elements ◽  
Dry Land ◽  
Fluid Reabsorption ◽  
Collecting Ducts ◽  
Urine Formation

The evolution of the kidney has had a major role in the emigration of vertebrates from the sea onto dry land. The mammalian kidney has conserved to a remarkable extent many of the molecular and functional elements of primordial apocrine kidneys that regulate fluid balance and eliminate potentially toxic endogenous and xenobiotic molecules in the urine entirely by transepithelial secretion. However, these occult secretory processes in the proximal tubules and collecting ducts of mammalian kidneys have remained underappreciated in the last half of the twentieth century as investigators focused, to a large extent, on the mechanisms of glomerular filtration and tubule sodium chloride and fluid reabsorption. On the basis of evidence reviewed in this paper, we propose that transepithelial salt and fluid secretion mechanisms enable mammalian renal tubules to finely regulate extracellular fluid volume and composition day to day and maintain urine formation during the cessation of glomerular filtration.

Osmotic forces driving water reabsorption in the proximal tubule of the rat kidney

1989 ◽  
Vol 257 (4) ◽  
pp. F669-F675 ◽  
Author(s):  
R. Green ◽  
G. Giebisch
Keyword(s):  
Reflection Coefficient ◽  
Water Permeability ◽  
Rat Kidney ◽  
Proximal Tubules ◽  
Osmotic Gradient ◽  
Water Reabsorption ◽  
Fluid Flux ◽  
Fluid Reabsorption ◽  
Ionic Fluxes ◽  
Peritubular Capillaries

Simultaneous microperfusion of proximal tubules and peritubular capillaries in kidneys of rats anesthetized with Inactin was used to measure reabsorption of fluid in response to an imposed osmotic gradient. The tubular fluid was isotonic and the peritubular capillaries were made hypertonic with NaCl or NaHCO3. Mean gradients and ionic fluxes were measured. When no gradient was imposed tubular fluid became hypotonic and rate of fluid reabsorption was 0.700 nl.mm-1.min-1. Imposition of a 25 mM NaCl gradient increased fluid flux to 3.887 nl.mm-1.min-1, whereas 25 mM NaHCO3 stimulated 5.226 ml/mm fluid reabsorption. This gave a relative reflection coefficient of NaCl:NaHCO3 of 0.73. Apparent water permeability varied with highest values for the smallest gradients. This suggests the possibility of a compartment in the epithelium that is hypertonic to the peritubular capillaries. The hypertonicity required to account for fluid movement was 6-16 mosmol/kg.

Luminal hypotonicity in proximal tubules of aquaporin-1-knockout mice

2000 ◽  
Vol 278 (6) ◽  
pp. F1030-F1033 ◽  
Author(s):  
V. Vallon ◽  
A. S. Verkman ◽  
J. Schnermann
Keyword(s):  
Knockout Mice ◽  
Chloride Concentration ◽  
Plasma Osmolality ◽  
Proximal Tubules ◽  
Fluid Absorption ◽  
Wild Type ◽  
Fluid Reabsorption ◽  
Aquaporin 1 ◽  
Proximal Tubular

To examine the role of aquaporin-1 (AQP1) in near-isosmolar fluid reabsorption in the proximal tubule, we compared osmolalities in micropuncture samples of late proximal tubular fluid and plasma in wild-type (+/+) and AQP1-knockout (−/−) mice. Compared with matched wild-type mice, the −/− animals produce a relatively hypotonic urine (607 ± 42 vs. 1,856 ± 101 mosmol/kgH2O) and have a higher plasma osmolality under micropuncture conditions (346 ± 11 vs. 318 ± 5 mosmol/kgH2O; P < 0.05). Measurements of tubular fluid osmolality were done in three groups of mice, +/+, −/−, and hydrated −/− mice in which plasma osmolality was reduced to 323 ± 1 mosmol/kgH2O. Late proximal tubular fluid osmolalities were 309 ± 5 (+/+, n= 21), 309 ± 4 (−/−, n = 24), and 284 ± 3 mosmol/kgH2O (hydrated −/−, n = 19). Tubular fluid chloride concentration averaged 152 ± 1 (+/+), 154 ± 1 (−/−), and 140 ± 1 mM (hydrated −/−). Transtubular osmotic gradients in untreated and hydrated AQP1 −/− mice were 39 ± 4 ( n = 25) and 39 ± 3 mosmol/kgH2O ( n = 19), values significantly higher than in +/+ mice (12 ± 2 mosmol/kgH2O; n = 24; both P < 0.001). AQP1 deficiency in mice generates marked luminal hypotonicity in proximal tubules, resulting from the retrieval of a hypertonic absorbate and indicating that near-isosmolar fluid absorption requires functional AQP1.

Microperfusion study of fluid reabsorption in proximal tubules of rat kidneys

1967 ◽  
Vol 213 (3) ◽  
pp. 809-818 ◽  
Author(s):  
M Wiederholt ◽  
K Hierholzer ◽  
EE Windhager ◽  
G Giebisch
Keyword(s):  
Proximal Tubules ◽  
Fluid Reabsorption ◽  
Rat Kidneys

Measurement of chloride movement across single proximal tubules of Necturus kidney

1963 ◽  
Vol 204 (3) ◽  
pp. 387-391 ◽  
Author(s):  
Gerhard Giebisch ◽  
Erich E. Windhager
Keyword(s):  
Carboxylic Acid ◽  
Chloride Concentration ◽  
Proximal Tubules ◽  
Electrochemical Potential ◽  
Potential Difference ◽  
Fluid Reabsorption ◽  
Ringer’S Solution ◽  
Electrometric Titration ◽  
The Relationship ◽  
Significant Concentration

To study the relationship between chloride fluxes and electrochemical potential difference, single proximal tubules of Necturus were perfused with a modified Ringer's solution containing Cl36. Collected fluid samples were assayed for radioactivity of inulin-C14 carboxylic acid and of Cl36, and chloride concentration was measured by electrometric titration. No significant concentration gradient for chloride was observed while inulin concentration ratios significantly above unity indicated fluid reabsorption. The results indicate that net reabsorptive chloride movement represents only a small fraction of chloride efflux. The relationship between chloride outflux/influx ratio and transtubular electrochemical potential difference is tentatively interpreted as indicating that reabsorptive chloride movement is passive in nature.

A new microelectrode method for simultaneous measurement of pH and PCO2

1986 ◽  
Vol 251 (5) ◽  
pp. F933-F937 ◽  
Author(s):  
K. Bomsztyk ◽  
M. B. Calalb
Keyword(s):  
Chemical Equilibrium ◽  
Simultaneous Measurement ◽  
Liquid Membrane ◽  
Renal Cortex ◽  
Serum Proteins ◽  
Proximal Tubules ◽  
Arterial Pco2 ◽  
Arterial Blood ◽  
Peritubular Capillaries ◽  
Anionic Composition

A liquid-membrane pH-PCO2 microelectrode is described for the simultaneous measurement of pH and PCO2 in tissues and body fluids. The microelectrode is simple and easy to fabricate. It can be used to measure HCO3 concentration in solutions at chemical equilibrium. In the physiological range the microelectrode response is linear with nearly Nernstian slopes for PCO2 (61.2 +/- 2.0 mV/log10 PCO2) and pH (63.7 +/- 1.9 mV/pH units) (n = 14) at 37 degrees C. The PCO2 response is independent of the solutions' pH, anionic composition, and presence of serum proteins. In randomly micropunctured rat surface proximal tubules, pH averaged 6.80 +/- 0.04 and PCO2 averaged 57.7 +/- 4.6 mmHg (n = 22), whereas in the adjacent peritubular capillaries pH was higher (7.27 +/- 0.03) but PCO2 was not different (55.7 +/- 4.6 mmHg) (n = 22). Systemic arterial PCO2 was significantly lower compared with the renal cortex and averaged 37.4 +/- 2.4 mmHg (n = 14). Directly measured and pH-PCO2 microelectrode-derived HCO3 concentrations in systemic arterial blood, surface fluid bathing the kidney, and randomly micropunctured proximal tubules were approximately equal.

Tubule urate and PAH transport: sensitivity and specificity of serum protein inhibition

1987 ◽  
Vol 252 (4) ◽  
pp. F683-F690
Author(s):  
J. J. Grantham ◽  
J. Kennedy ◽  
B. Cowley
Keyword(s):  
Bovine Serum ◽  
Plasma Proteins ◽  
Gamma Globulin ◽  
Serum Proteins ◽  
Organic Anion ◽  
Proximal Tubules ◽  
Rabbit Serum ◽  
Inhibitory Effects ◽  
Protein Inhibition ◽  
External Face

Macromolecules in rabbit serum inhibit the cellular uptake and transepithelial secretion of [14C]urate and p-[3H]aminohippurate ([3H]PA) in rabbit S2 proximal tubule segments. To understand better the potential role these inhibitors may have in the regulation of renal organic anion excretion, we examined the specificity and relative inhibitory effects on tubule urate and PAH transport of albumin and gamma-globulin, the major inhibitory proteins in rabbit serum. Native rabbit serum markedly inhibited the cellular accumulation of urate and PAH by isolated nonperfused segments [50% inhibition (K0.5) = 0.4 and 0.65 g/dl, respectively]. Urate and PAH transport was also inhibited by bovine serum, human serum, Cohn-fractionated rabbit albumin, and rabbit gamma-globulin, but not by Cohn-fractionated bovine serum albumin. alpha-Lactalbumin and beta-lactoglobulin, derived from milk, also inhibited urate and PAH transport, but to a lesser extent than albumin and gamma-globulin. The transport inhibitory effects of proteins were independent of their binding to urate and PAH. Unidirectional influx and the steady-state intracellular accumulation of urate and PAH in suspensions of proximal tubules were decreased by rabbit serum proteins, suggesting that these inhibitors act on the external face of the cells to diminish the uptake of the organic anions. These studies indicate that the principal plasma proteins (albumin and gamma-globulin) significantly inhibit urate and PAH transporters in the basolateral membranes of S2 proximal tubules. We suggest that circulating plasma proteins that can penetrate the basement membrane of proximal tubules may directly modulate the renal excretion of urate and PAH.

Luminal hypotonicity: a driving force for fluid absorption from the proximal tubule

1984 ◽  
Vol 246 (2) ◽  
pp. F167-F174 ◽  
Author(s):  
R. Green ◽  
G. Giebisch
Keyword(s):  
Reflection Coefficient ◽  
Driving Force ◽  
Proximal Tubules ◽  
Tubular Epithelium ◽  
Fluid Absorption ◽  
Fluid Reabsorption ◽  
Hypotonic Fluid ◽  
Peritubular Capillaries ◽  
Proximal Tubular ◽  
Proximal Tubular Epithelium

The ability of rat proximal tubules to generate a hypotonic luminal fluid was investigated. Simultaneous perfusion of tubules and peritubular capillaries was performed with simple solutions. When tubules were perfused at 10 nl X min-1 and NaCl was the perfusate for tubules and capillaries, solute and fluid (0.41 nl X min-1 X mm-1) were transported and the luminal fluid became hypotonic (delta osmol = -1.7 mosmol X kg-1). When the same solutions were used but the tubule was perfused at 45 nl X min-1, more fluid (0.89 nl X min-1 X mm-1) was reabsorbed and the fluid became more hypotonic (delta osmol = -3.9 mosmol X kg-1). Bicarbonate in the peritubular capillaries increased the fluid reabsorption (1.21 nl X min-1 X mm-1) but did not generate cryoscopically hypotonic fluid. Cyanide abolished all net movement of fluid and solute. It is concluded that the tubule can generate a hypotonic fluid, that the hydraulic conductivity for proximal tubular epithelium is 3,200-3,400 microns X s-1, and that the reflection coefficient for NaHCO3 is slightly higher than for NaCl.

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