The proximal straight tubule (PST) basolateral cell membrane water channel: Selectivity characteristics

1995 ◽  
Vol 143 (3) ◽  
Author(s):  
A.M. Guti�rrez ◽  
E. Gonz�lez ◽  
M. Echevarr�a ◽  
C.S. Hern�ndez ◽  
G. Whittembury
Keyword(s):  
Cell Membrane ◽  
Water Channel ◽  
Straight Tubule ◽  
Basolateral Cell Membrane ◽  
Channel Selectivity ◽  
Proximal Straight Tubule

Defective water and glycerol transport in the proximal tubules of AQP7 knockout mice

2005 ◽  
Vol 289 (6) ◽  
pp. F1195-F1200 ◽  
Author(s):  
Eisei Sohara ◽  
Tatemitsu Rai ◽  
Jun-ichi Miyazaki ◽  
A. S. Verkman ◽  
Sei Sasaki ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Water Channel ◽  
Physiological Role ◽  
Wild Type ◽  
Double Knockout ◽  
Straight Tubule ◽  
Glycerol Transport ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Urinary Concentrating Ability

The aquaporin-7 (AQP7) water channel is known as a member of the aquaglyceroporins, which facilitate the transport of glycerol as well as water. Although AQP7 is abundantly expressed on the apical membrane of the proximal straight tubules in the kidney, the physiological role of AQP7 is still unknown. To investigate this, we generated AQP7 knockout mice. The water permeability of the proximal tubule brush-border membrane measured by the stopped-flow method was slightly but significantly reduced in the AQP7 knockout mice compared with that of wild-type mice (AQP7, 18.0 ± 0.4 × 10−3 cm/s vs. wild-type, 20.0 ± 0.3 × 10−3 cm/s). Although AQP7 solo-knockout mice did not exhibit a urinary concentrating defect, AQP1/AQP7 double-knockout mice had a reduction in urinary concentrating ability compared with AQP1 solo-knockout mice, suggesting that the amount of water reabsorbed through AQP7 in the proximal straight tubules is physiologically substantial. On the other hand, AQP7 knockout mice showed marked glyceroluria (AQP7, 1.7 ± 0.34 mg/ml vs. wild-type, 0.005 ± 0.002 mg/ml). This identified a novel glycerol reabsorption pathway in the proximal straight tubules. In two mouse models of proximal straight tubule injury, the cisplatin-induced acute renal failure (ARF) model and the ischemic ARF model, an increase in urine glycerol was observed (pretreatment, 0.007 ± 0.005 mg/ml; cisplatin, 0.063 ± 0.043 mg/ml; ischemia, 0.076 ± 0.02 mg/ml), suggesting that urine glycerol could be used as a new biomarker for detecting proximal straight tubule injury.

scholarly journals QUANTITATIVE HISTOCHEMISTRY OF URIDINE DIPHOSPHOGLUCOSE-PYROPHOSPHATASE AND URIDINE DIPHOSPHOGLUCOSE-PYROPHOSPHORYLASE IN DEVELOPING RAT KIDNEY

1974 ◽  
Vol 22 (11) ◽  
pp. 1034-1038 ◽  
Author(s):  
CLINTON N. CORDER ◽  
MARK L. BERGER ◽  
OLIVER H. LOWRY
Keyword(s):  
Rat Kidney ◽  
Development Activity ◽  
Quantitative Histochemistry ◽  
Small Arteries ◽  
Straight Tubule ◽  
Adult Kidney ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Developing Rat ◽  
Made In

Quantitative histochemical measurements of two enzymes of uridine diphosphoglucose (UDPG) metabolism have been made in the developing rat kidney nephron. Kidneys were examined from -4 days to 44 days of age. In the adult kidney, UDPG-pyrophosphatase was concentrated in proximal convoluted and straight tubules. During maturation, activity decreased in glomeruli, increased in the proximal tubule and changed little elsewhere in the nephron. UDPG-pyrophosphorylase revealed a different pattern. Activity was more nearly uniformly distributed throughout the nephron but was highest in the proximal straight tubule and ascending limb of Henle. During development, activity was unchanged or increased in glomeruli and small arteries and increased elsewhere, particularly in the proximal straight tubule and ascending limb of Henle.

Vitamin D3 metabolites increase [Ca2+]i in rabbit renal proximal straight tubule cells

1991 ◽  
Vol 260 (5) ◽  
pp. F757-F763 ◽  
Author(s):  
M. Suzuki ◽  
S. Kurihara ◽  
Y. Kawaguchi ◽  
O. Sakai
Keyword(s):  
Vitamin D ◽  
Proximal Tubule ◽  
Ion Concentration ◽  
Rabbit Kidney ◽  
Vitamin D Metabolites ◽  
Dihydroxyvitamin D3 ◽  
Straight Tubule ◽  
Proximal Straight Tubule ◽  
Tubule Cells ◽  
Free Media

Vitamin D metabolites exert both acute and chronic influences on proximal tubule function. To further evaluate vitamin D action on the kidney, we examined the immediate effects of vitamin D metabolites on cytoplasmic calcium ion concentration [( Ca2+]i), using fura-2 and patch-clamp method in cultured proximal straight tubule cells of rabbit kidney. 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] and 25-hydroxyvitamin D3 [25(OH)D3] evoked a transient rise in [Ca2+]i, and 24,25-dihydroxyvitamin D3 [24,25(OH)2D3] caused a sustained rise in [Ca2+]i; all effects were dose dependent. [Ca2+]i transient, evoked by 1,25(OH)2D3 alone, was abolished in Ca(2+)-free media. Pretreatment of cells in Ca(2+)-free media with caffeine (4 mM) or ryanodine (1 microM) to deplete Ca2+ store of endoplasmic reticulum or with TMB-8 (5 mM) to block Ca2+ release from storage blunted the effect of 25(OH)D3 on [Ca2+]i but not of 24,25(OH)2D3. Data were also supported by activities of Ca-dependent K channel and show that these three vitamin D metabolites in pharmacological doses increase [Ca2+]i of proximal tubule cells from different sources.

The collecting tubule of Amphiuma. I. Electrophysiological characterization

1987 ◽  
Vol 253 (6) ◽  
pp. F1263-F1272 ◽  
Author(s):  
M. Hunter ◽  
J. D. Horisberger ◽  
B. Stanton ◽  
G. Giebisch
Keyword(s):  
Cell Membrane ◽  
Cell Model ◽  
Basolateral Membrane ◽  
Apical Cell ◽  
Potassium Conductance ◽  
Sodium Reabsorption ◽  
Apical Cell Membrane ◽  
Cation Selectivity ◽  
Basolateral Cell Membrane ◽  
Collecting Tubules

Single collecting tubules of Amphiuma kidneys were perfused in vitro to characterize their electrophysiological properties. The lumen-negative potential (-24 mV) was abolished by amiloride in the lumen and by ouabain in the bath. Ion substitution experiments in the lumen demonstrated the presence of a large sodium conductance in the apical cell membrane, but no evidence was obtained for a significant potassium or chloride conductance. Ion substitutions in the bath solution and the depolarizing effect of barium on the basolateral membrane potential demonstrated the presence of a large potassium conductance in the basolateral cell membrane. Measurements of dilution potentials in amiloride-treated tubules revealed a modest cation selectivity of the paracellular pathway. These results support a cell model in which sodium reabsorption occurs by electrodiffusion across the apical cell membrane and active transport across the basolateral cell membrane. The absence of a detectable potassium conductance in the apical cell membrane suggests that secretion of this ion cannot take place by diffusion from cell to lumen.

Conductive properties of the rabbit outer medullary collecting duct: inner stripe

1985 ◽  
Vol 248 (4) ◽  
pp. F500-F506 ◽  
Author(s):  
B. M. Koeppen
Keyword(s):  
Cell Membrane ◽  
Collecting Duct ◽  
Basolateral Membrane ◽  
Apical Cell ◽  
Rabbit Kidney ◽  
Apical Cell Membrane ◽  
Basolateral Cell Membrane ◽  
Medullary Collecting Duct ◽  
Conductive Properties

Segments of outer medullary collecting duct were dissected from the inner stripe of the rabbit kidney (OMCDi) and perfused in vitro. The conductive properties of the tubule epithelium and individual cell membranes were determined by means of cable analysis and intracellular voltage-recording microelectrodes. In 35 tubules the transepithelial voltage (VT) and resistance (RT) averaged 17.2 +/- 1.4 mV, lumen positive, and 58.6 +/- 5.3 k omega X cm, respectively. The basolateral membrane voltage, (Vbl) was -29.2 +/- 2.1 mV (n = 23). The apical cell membrane did not contain appreciable ion conductances, as evidenced by the high values of apical cell membrane fractional resistance (fRa = Ra/Ra + Rb), which approached unity (0.99 +/- 0.01; n = 23). Moreover, addition of amiloride or BaCl2 to the tubule lumen was without effect on the electrical characteristics of the cell, as was a twofold reduction in luminal [Cl-]. The conductive properties of the basolateral cell membrane were assessed with bath ion substitutions. A twofold reduction in bath [Cl-] depolarized Vbl by 14.7 +/- 0.4 mV (theoretical, 17 mV), while a 10-fold increase in bath [K+] resulted in only a 0.9 +/- 0.4 mV depolarization (theoretical, 61 mV). Substituting bath Na+ with tetramethylammonium (from 150 to 75 mM) was without effect. Reducing bath [HCO-3] from 25 to 5 mM (constant PCO2) resulted in a steady-state depolarization of Vbl of 8.4 +/- 0.4 mV that could not be attributed to conductive HCO-3 movement. Thus, the basolateral cell membrane is predominantly Cl- selective.(ABSTRACT TRUNCATED AT 250 WORDS)

Transport of potassium in the rabbit pars recta

1982 ◽  
Vol 242 (3) ◽  
pp. F226-F237 ◽  
Author(s):  
J. Work ◽  
S. L. Troutman ◽  
J. A. Schafer
Keyword(s):  
Bathing Solution ◽  
Passive Permeability ◽  
Straight Tubule ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Pars Recta ◽  
K Secretion ◽  
Unidirectional Fluxes ◽  
K Concentration ◽  
K Permeability

Unidirectional fluxes of 42K+ and 86Rb+ were measured in isolated perfused segments of proximal straight tubules and no differences were found between the two isotopes for the same flux determination. In the three segments examined (the early and late superficial proximal straight tubule and the juxtamedullary proximal straight tubule) there was apparent net active K+ secretion as demonstrated by differences in the unidirectional fluxes of 2.6, 3.2, and 4.8 pmol.min-1.mm-1, respectively. However, in contrast to the expectations for active K+ secretion, the bath-to-lumen fluxes were unaffected by 0.1 mM ouabain added to the bathing solution, and in the early superficial and juxtamedullary segments these fluxes were directly proportional to the K+ concentration of the bathing solution over a range of concentrations. Apparent K+ permeability coefficients were calculated from lumen-to-bath fluxes to be 0.14 +/- 0.02, 0.10 +/- 0.02, and 0.52 +/- 0.07 micrometers.s-1 in the early and late superficial and juxtamedullary segments, respectively. Based on these data and on a mathematical analysis, we have concluded that active K+ secretion of the magnitude measured would have little importance in determining the K+ load delivered to the descending limb of the loop of Henle. However, the higher passive permeability of the juxtamedullary segment would allow significant net K+ secretion if the outer medullary interstitium had even a moderately elevated K+ concentration.

Polarity of alveolar epithelial cell acid-base permeability

2002 ◽  
Vol 282 (4) ◽  
pp. L675-L683 ◽  
Author(s):  
Dilip Joseph ◽  
Omar Tirmizi ◽  
Xiao-Ling Zhang ◽  
Edward D. Crandall ◽  
Richard L. Lubman
Keyword(s):  
Cell Membrane ◽  
Intracellular Ph ◽  
Short Circuit ◽  
Short Circuit Current ◽  
Ph Gradient ◽  
Acid Base ◽  
Alveolar Epithelial ◽  
Basolateral Cell Membrane ◽  
Fluid Compartments ◽  
Two Fluid

We investigated acid-base permeability properties of electrically resistive monolayers of alveolar epithelial cells (AEC) grown in primary culture. AEC monolayers were grown on tissue culture-treated polycarbonate filters. Filters were mounted in a partitioned cuvette containing two fluid compartments (apical and basolateral) separated by the adherent monolayer, cells were loaded with the pH-sensitive dye 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein, and intracellular pH was determined. Monolayers in HCO[Formula: see text]-free Na+ buffer (140 mM Na+, 6 mM HEPES, pH 7.4) maintained a transepithelial pH gradient between the two fluid compartments over 30 min. Replacement of apical fluid by acidic (6.4) or basic (8.0) buffer resulted in minimal changes in intracellular pH. Replacement of basolateral fluid by acidic or basic buffer resulted in transmembrane proton fluxes and intracellular acidification or alkalinization. Intracellular alkalinization was blocked ≥80% by 100 μM dimethylamiloride, an inhibitor of Na+/H+exchange, whereas acidification was not affected by a series of acid/base transport inhibitors. Additional experiments in which AEC monolayers were grown in the presence of acidic (6.4) or basic (8.0) medium revealed differential effects on bioelectric properties depending on whether extracellular pH was altered in apical or basolateral fluid compartments bathing the cells. Acid exposure reduced (and base exposure increased) short-circuit current from the basolateral side; apical exposure did not affect short-circuit current in either case. We conclude that AEC monolayers are relatively impermeable to transepithelial acid/base fluxes, primarily because of impermeability of intercellular junctions and of the apical, rather than basolateral, cell membrane. The principal basolateral acid exit pathway observed under these experimental conditions is Na+/H+ exchange, whereas proton uptake into cells occurs across the basolateral cell membrane by a different, undetermined mechanism. These results are consistent with the ability of the alveolar epithelium to maintain an apical-to-basolateral (air space-to-blood) pH gradient in situ.

Inhibition of Jv by ANF in rat proximal straight tubules requires angiotensin

1989 ◽  
Vol 257 (5) ◽  
pp. F907-F911 ◽  
Author(s):  
J. L. Garvin
Keyword(s):  
Angiotensin Ii ◽  
Atrial Natriuretic Factor ◽  
Second Messenger ◽  
Fluid Absorption ◽  
Straight Tubule ◽  
Cyclic Monophosphate ◽  
Natriuretic Factor ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Messenger System

The effects of atrial natriuretic factor (ANF) on fluid absorption (Jv) by isolated perfused proximal straight tubules of rats were investigated. ANF alone (10(-8) M) added to the bath had no significant effect on absorption. In contrast, when tubules were first treated with 1.6 X 10(-10) M angiotensin II, this same concentration of ANF lowered fluid absorption from 0.99 +/- 0.03 to 0.69 +/- 0.02 nl.mm-1.min-1. A lower dose of ANF, 2 X 10(-10) M, reduced fluid absorption in the presence of angiotensin II from 1.13 +/- 0.06 to 0.65 +/- 0.05 nl.mm-1.min-1, an inhibition of 40%. Since guanosine 3',5'-cyclic monophosphate (cGMP) is reportedly part of the second messenger system of ANF, the effects of dibutyryl-cGMP (DBcGMP) on fluid absorption were studied. This membrane-permeant form of cGMP mimicked the effects of ANF, reducing fluid absorption from 1.15 +/- 0.18 to 0.54 +/- 0.08 nl.mm-1.min-1. These studies suggested the following: 1) ANF can regulate fluid absorption in the proximal nephron; 2) this inhibition occurs only in the presence of angiotensin; and 3) cGMP is part of the second messenger system of ANF in the rat proximal straight tubule, as it is in other tissues.

Bicarbonate and ammonia transport in isolated perfused rat proximal straight tubules

1987 ◽  
Vol 253 (2) ◽  
pp. F277-F281 ◽  
Author(s):  
J. L. Garvin ◽  
M. A. Knepper
Keyword(s):  
Fluid Transport ◽  
Distal Tubule ◽  
Co2 Absorption ◽  
Straight Tubule ◽  
Straight Tubules ◽  
Proximal Straight Tubule ◽  
Total Ammonia ◽  
The Mean ◽  
Disequilibrium Ph

Bicarbonate, ammonia, and fluid transport were studied in isolated perfused proximal straight tubules from rats. The mean rate of fluid absorption (0.77 nl X min-1 X mm-1) and the mean rate of total CO2 absorption (42 pmol X min-1 X mm-1) exceeded corresponding rates measured previously in rabbit proximal straight tubules. The limiting total CO2 concentration when the tubules were perfused at slow flow rates was 5 mM, a value similar to those reported previously for rat proximal convoluted tubules and thick ascending limbs. When rat proximal straight tubules were perfused and bathed with solutions containing 1 mM total ammonia at slow perfusion rates, the measured total ammonia concentration in collected fluid rose to a level predicted by the diffusion trapping model of ammonia secretion in the absence of a luminal disequilibrium pH. We conclude the proximal straight tubule of the rat can absorb bicarbonate at a rate that can account for a large portion of the bicarbonate absorption measured in vivo between the late proximal convoluted tubule and the early distal tubule, the rat proximal straight tubule is capable of transepithelial ammonia secretion, most likely by NH3 diffusion down a concentration gradient generated by luminal acidification, and the rat proximal straight tubule apparently does not generate a luminal disequilibrium pH despite the occurrence of proton secretion, implying the presence of endogenous luminal carbonic anhydrase.

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