NaCl Permeability Research Articles

Effect of varying salt and urea permeabilities along descending limbs of Henle in a model of the renal medullary urine concentrating mechanism

Modelling studies have played an important role in research on the mechanism of urine concentration and dilution by the medulla of the kidney ever since Hargitay and Kuhn (1951, Z. Elektrochem. 55, 539–558) first proposed that the parallel tubular structures in the kidney medulla must function as a “countercurrent multiplication” system. Present-day models, in keeping with our considerably improved understanding of most aspects of medullary structure-function relationships, have evolved into rather sophisticated systems of parallel tubes. In spite of this increasing complexity, it has remained the case that “model medullas” do not concentrate as well as the real kidney, especially in the inner medulla where only passive, diffusional transport occurs. Inasmuch as these models take into account the majority of contemporary ideas making up our global hypothesis about the functioning of this system, their failure to behave physiologically indicates that our understanding remains incomplete. The purpose of the present modelling study was to evaluate the implications of some recent measurements showing that permeabilities of NaCl ( P s ) and urea ( P u ) vary along the length of the descending thin limbs of Henle (Imai et al., 1988, Am. J. Physiol. 254, F323–F328), rather than being constant throughout this segment as had been assumed earlier. It was hoped that these newly measured values might explain, by a passive, diffusional process, the net solute addition at the bend of Henle's loop observed under some circumstances and heretofore attributed (though without any supporting experimental evidence) to active transport into the descending limb. The results of the present study show that whereas incorporation of the new values for P s and P u in the descending limbs of short nephrons does indeed improve the concentrating power of the model, these new values are nonetheless not sufficient to allow the model to build an osmolarity gradient that increases all the way through the inner medulla. This failing, which is common to virtually all modelling studies to date using measured values from rat kidneys, probably points to a key role for preferential exchange supposed by some to exist among certain tubule segments within vascular bundles in species whose kidneys have the highest concentrating power.

Model study of placental water transfer and causes of fetal water disease in sheep

The purpose of the computer simulation was to use experimentally measured parameters of placental water transfer to compute conceptual water acquisition during the last third of ovine pregnancy and to evaluate the possible role of each of these parameters in the pathophysiology of polyhydramnios. Total conceptual water at birth was almost insensitive to the value of the placental filtration coefficient. It was more sensitive to fetal and maternal placental blood flows, the concentrations of actively transported or metabolically produced solutes in fetal plasma (bicarbonate, fructose, alpha-amino acids, urea, lactate), and the hydrostatic pressure difference across the placental barrier. It was quite sensitive to the NaCl reflection coefficient and permeability. We conclude that the actively transported or produced solutes in fetal plasma constitute a primary driving force. The opposing diffusion gradient of NaCl, and to a much lesser extent that of glucose, are essential to restrain the process. The causes of polyhydramnios in this species are, in order of probability, an increase in the placental diffusion permeability of NaCl, a decrease in the placental reflection coefficient for NaCl, or an increase in the concentration of an osmotically effective solute in fetal plasma, by active transport or metabolic production.

Measurement of transport properties of poly(methylmethacrylate-co-methacrylic acid) ion-containing membranes

Several membranes prepared from poly(methylmethacrylate-co-methacrylic acid) and its Li+ and Zn2+ ionomers were tested for NaCl, creatinine and urea permeability. The permeabilities of the membranes were explained on the basis of pore contents determined from their scanning electron microscope micrographs. All the membranes showed higher permeabilities during the first 2 hours of experimentation. Introduction of Zn2+ ions into the copolymer as crosslinking agent did not have much effect on the membrane properties but the properties of the copolymer were modified.

Chloride and osmotic water permeabilities of isolated rabbit renal papillary surface epithelium

The papillary surface epithelium (PSE) covers the mammalian renal papilla. It has been proposed that water or solute fluxes across the PSE might result in changes in urine or medullary interstitial fluid composition. To study osmotic water and chloride permeabilities, the PSE was dissected from underlying medullary tissue and mounted in a small Ussing chamber. Osmotic water permeability was low (14.2 +/- 3.0 microns/s) and was unaffected by 100 nM vasopressin added to the basolateral surface. In contrast, the PSE showed a substantial chloride permeability of 3.1 +/- 0.4 x 10(-5) cm/s that decreased reversibly to 2.2 +/- 0.3 x 10(-5) cm/s (P less than 0.01) with vasopressin. Vasopressin also reversibly increased the transepithelial resistance of the PSE from 87 +/- 9 to 106 +/- 13 omega.cm2 (P less than 0.02). Apical bumetanide (10(-6) M) had no significant effect on PSE chloride permeability. The apparent Na-Cl permeability ratio (0.75 +/- 0.01) calculated from dilution potential measurements was not affected significantly by vasopressin or apical bumetanide. We conclude that it is unlikely that physiologically significant osmotic water fluxes occur across the papillary surface epithelium. However, the NaCl permeability is sufficiently high that physiologically significant transepithelial NaCl fluxes could occur under conditions associated with reflux of urine backward from the papillary tip.

Plasma‐modified Nylon 4 membrane for dialysis

AbstractThe effects of plasma treatment conditions, such as supply power, treatment time, gases used in reactor, surface energy, water content, dialysis permeability, partition coefficient, diffusion coefficient, and free volume of Nylon 4 membranes, were studied. The solutes considered for dialysis system were NaCl, urea, and MgCl2. The permeabilities of NaCl and urea of membranes with plasma treated in argon at 80 W for 20 min are 5.57 × 10−5 and 5.89 × 10−5 cm2/min, respectively. Much higher permeabilities of NaCl and urea obtained by oxygen plasma‐treated membranes under 20 W and for 20 min are 30.74 × 10−5 and 17.66 10−5 cm2/min, respectively, compared to that of untreated Nylon 4 membranes.

Hormone effects on NaCl permeability of rat inner medullary collecting duct.

It has been proposed that regulation of NaCl excretion occurs in part by hormonal effects on NaCl permeability in the inner medullary collecting duct (IMCD). We carried out experiments in isolated perfused terminal IMCDs to determine whether atrial natriuretic factor (ANF), vasopressin, or deoxycorticosterone (DOC) affects NaCl permeability. Apparent Cl- or Na+ permeabilities (PCl and PNa) were determined by measuring ion fluxes resulting from imposed electrochemical gradients. Transepithelial resistance (RT) was calculated from voltage deflections at the perfusion and collection ends of the tubule, which resulted from perfusion end current injection (cable analysis). ANF [rat ANF-(1-28), 100 nM in the peritubular bath] significantly decreased PCl from 2.20 to 1.84 x 10(-5) cm/s and did not alter PNa (1.11 to 1.18 x 10(-5) cm/s). ANF also decreased PCl in IMCDs from DOC-treated rats (1.14 to 0.98 x 10(-5) cm/s). Vasopressin (10 nM in the peritubular bath) did not affect PCl. RT averaged 39.3 omega.cm2 in IMCDs from control rats and was significantly increased to 62.3 omega.cm2 in tubules from DOC-treated rats. Neither ANF nor vasopressin significantly affected RT in either group. We conclude the following: 1) the results do not support the hypothesis that ANF causes natriuresis by increasing the NaCl permeability of the terminal IMCD. Instead, ANF significantly decreases the chloride permeability. 2) Vasopressin does not affect NaCl permeability. 3) Mineralocorticoid-induced antinatriuresis may be due in part to reduced NaCl permeability in the terminal IMCD.

Thick ascending limb response to dDAVP and atrial natriuretic factor in vivo.

Because of the inaccessibility of the thick ascending limb (TAL) to micropuncture, it has been difficult to evaluate the effects of ADH and atrial natriuretic factor (ANF) on TAL salt transport in vivo. The purpose of the present study is to assess the effects of these hormones on TAL NaCl reabsorption in vivo. Although passive NaCl permeability and unidirectional Na fluxes were not measured, the microstop-flow conductivity technique that was used in these studies controls solute delivery, permits the measurement of the rate of net NaCl reabsorption, and tests the capacity of the TAL to establish a limiting gradient. Despite the presence of a dramatic natriuretic response, a natural extract of ANF did not significantly increase the minimum NaCl concentration reached by the TAL after 60 s of stop-flow. However, 1-[desamino]-8-D-arginine vasopressin (dDAVP) increased by 23%, the rate at which luminal Na concentration declined, and reduced by 28% the minimum NaCl concentration achieved by the TAL. Therefore, these results do not demonstrate a significant direct peritubular effect of ANF on TAL NaCl permeability in outer cortical nephrons, but support a role for antidiuretic hormone in enhancing TAL NaCl reabsorption in vivo.

Functional capsule membranes. Part 29. Concanavalin A-induced permeability control of capsule membranes corked with synthetic glycolipid bilayers or grafted with synthetic glycopolymers

Large, ultrathin nylon capsule membranes were corked with synthetic glycolipid (2C14-glu and 2C14-gal) or grafted with synthetic polymers having pendant saccharides (Poly-glu and Poly-gal). The permeability of NaCl from the capsule corked with glycolipid bilayers having the α-D-glucopyranosyl head group, but not the β-D-galactopyranosyl head group, was increased by interaction with concanavalin A (Con A) because of the distortion of corking bilayers induced by the specific binding of Con A to the α-D-glucopyranosyl head group on the capsule surface. When the capsule grafted with polymers having pendant α-D-glucopyranosyl units, but not β-D-galactopyranosyl units, was employed, the permeability of water-soluble dyes was reversibly reduced and increased by the alternative addition of Con A and an excess of monosaccharides from outside, respectively. Thus, Con A could specifically form the cross-linked complex with the α-D-glucopyranosyl unit of graft-polymers on the capsule surface and could reduce the permeability. Upon addition of an excess of monosaccharides, Con A was removed from the capsule surface and the permeability reverted to the original fast rate. These permeability changes with Con A largely depend on the molecular size of the permeants. Thus, the lipid bilayers or graft-polymers on the capsule membrane was found to act as a permeation value responding to specific molecular recognition between lectins and carbohydrates on the membrane surface.

Control of solute permeability based on pH‐induced reversible conformational change in block copolypeptide membrane

AbstractAn ABBA‐type block copolypeptide membrane composed of L‐glutamic acid (A) and L‐leucine (B) was prepared, and a solute permeability of the membrane was studied. According to the observation of electron microscope, the membrane had the phase‐separated morphology that the domains consisting of poly(L‐glutamic acid) blocks are emebedded in a continuous matrix of the poly(L‐leucine) phase. The reversible conformational change of the poly(L‐glutamic acid) from α‐helix to random coil induced by changing the pH of the external medium was presumed to occur in the domains on the basis of the results of infrared absorption spectra. In the pH dependence of the diffusion coefficients of KCl, NaCl, and LiCl in the membrane, a considerable decrease was found at about pH 4, and thought to result from the conformational transition. In an acidic medium, the permeability of KCl, NaCl, and NiCl was higher then that of glucose, but this order was reversed in higher pHs. These results indicate that the poly(L‐glutamic acid) domains in the membrane function as channels for solute transport.

Salt permeation through cationic membranes with quaternary ammonium groups of different alkylchain lengths

Cationic membranes were prepared by quaternizing poly(chloromethylstyrene-codivinylbenzene) membrane with triethyl, tri-n-propyl and tri-n-octyl amines. The permeabilities of NaCl, NaBr, NaI and NaNO 3 were measured. The dependence of the permeabilities on the upstream salt concentration was not of a simple Donnan exclusion type, which is unusual. The permeability of the membrane quaternized with triethylamine for NaI showed a marked decrease with upstream salt concentration up to ca. 0.1 mol/l and leveled off thereafter. The permeability of the membrane quaternized with tri-n-propylamine for NaCl, NaBr and NaNO 3 showed minima at relatively low upstream salt concentrations. These results, together with the sorption isotherms, were qualitatively discussed in terms of dual sorption and diffusion modes of the salts

Membrane potentials and permeation of NaCl in poly(vinyl alcohol‐co‐itaconic acid) membranes

AbstractThe membrane potential and permeability of NaCl were measured for six crosslinked poly(vinyl alcohol‐co‐itaconic acid) membranes having various water contents [0.25≤H≤0.83 H2O (g)/swollen membrane (g)] and interpreted by means of an equation derived from Schlögl′s theory. Both results of the membrane potential and the permeability of the membranes having H≥0.34 could be satisfactorily interpreted by the theory. The permeability of NaCl in the membrane of H=0.25 gave, however, an increasing tendency with the decrease of the upstream concentration lower than 0.04 mol/L. It was considered that the concentration dependence reverse to what was caused by the Donnan exclusion might be due to the concentration dependence of the thermodynamic partition coefficient in nonfreezing water of the membrane. By the equation thus derived the membrane potential and the permeability of NaCl in the membrane of H=0.25 were expained qualitatively. The mobility ratios of Na+ and Cl− and the effective charge density in the membranes were discussed.

Permeation control by a phase transition of the dialkylsilane monolayer immobilized on a porous glass plate

The polymeric monolayer of dialkylsilane amphiphiles was covalently bonded onto a porous glass plate by the Langmuir–Blodgett technique, and the permeability of NaCl could be controlled by the phase transition of the immobilized monolayer.

Reverse Osmosis Separations of Aqueous NaCl–Organic Solute Systems

Abstract Some of alcohols, amides, aromatic hydrocarbons and surfactants were used as organic solute. Addition of NaCl increased the rejections of aromatic hydrocarbons and decreased the rejections of amides. It was also found that the permeability of NaCl was influenced by organic solutes.

Permeability characteristics of the rat urinary bladder in experimental cystitis and after overdistension.

The permeability characteristics of the rat urinary bladder were investigated in experimental cystitis achieved by xylene/Escherichia coli, after dimethylsulfoxide (DMSO) exposure and 3 and/or 10 days after overdistension. The changes were found to be comparable between experimental cystitis and DMSO treatment, whereas those after overdistension were specifically different in nature. Passive increases in NaCl permeability were shown to be accompanied by functional, metabolic impairment of the urothelium. It has been suggested that the concept of an almost impermeable 'blood-urine barrier' is completely misleading under these circumstances. This should be taken into account in future clinical considerations.

Bilayer-coated capsule membranes. IV. : Control of NaCl permeability by phase transition of synthetic bilayer coatings, depending on their hydrophilic head groups

Ultrathin nylon capsule membranes coated with synthetic bilayers, the hydrophilic head groups of which had cationic, anionic, zwitterionic and nonionic charges, were prepared. Permeation of NaCl trapped in the inner aqueous phase was reduced by a factor of 10-1000 relative to that of the uncoated, semipermeable capsules, and drastically changed at the phase transition temperature, T c, of the coating bilayers, depending on the charge of their hydrophilic head group. In the case of capsules coated with positively or negatively charged bilayers, NaCl permeation was enhanced at temperatures above the T c of the coating bilayers, as expected. On the other hand, NaCl release of capsules coated with neutral charged (nonionic and zwitterionic) bilayers was largely reduced at temperatures above the T c. From activation energy data of Arrhenius plots, the permeation mechanism of NaCl, depending on the membrane surface charge, below and above the T c was discussed.

The formation of stable transient pores across bilayer-coated capsule membranes by external electric fields

The permeability of NaCl from bilayer-coated capsule membranes is reversibly by an external electric field, because of the formation of stable transient pores in bilayers by transmembrane potentials.

Purification and Concentration of Betalaines by Ultrafiltration and Reverse Osmosis

ABSTRACTBeet juices prepared by solid‐liquid extractions were processed by ultrafiltration (UF) and reverse osmosis (RO) to 30°Brix at 20°C. De Danske Sukkerfabrikker (DDS) UF/RO Lab Module‐20 plate‐and‐frame system was used having a 0.72‐m2 effective membrane area and pressures from 50‐40 bar. After prefiltering, pectinase treated juices were sequentially processed through 20,000 and 6,000 (UF) molecular weight (MW) cut‐off membranes. The UF purified products were then concentrated by RO processes on several types of cellulose acetate (CA) membranes, one with a 500 MW cut‐off and 70% NaCl permeability provided colorants that were separated from a majority of soluble solids. Addition of invertase to pectinase‐treated juices decreased flux but yielded a three‐fold increase in betalaine concentration on a dry weight basis. Betalaine concentration by UF and RO processes also halved nitrate level and greatly reduced flavor.

NaCl transport in mouse medullary thick ascending limbs. I. Functional nephron heterogeneity and ADH-stimulated NaCl cotransport.

We assessed the effects of antidiuretic hormone and cyclic adenosine monophosphate (cAMP) analogues on transepithelial voltage, Ve, and/or net chloride absorption in isolated mouse medullary (mTALH) and cortical (cTALH) thick ascending limbs of Henle; the passive NaCl permeability characteristics and electrical properties of the mTALH; and the effects of anion and cation substitutions and transport inhibitors on both basal and ADH-stimulated Ve and/or net chloride absorption in the mTALH. The data demonstrate that these two segments are functionally heterogeneous: ADH, at concentrations comparable to plasma levels seen in mammalian species during ordinary antidiuresis, and/or cAMP increase three- to fourfold the rate of NaCl absorption in the mTALH but not in the cTALH. The ion substitution and inhibitor data are consistent with the view that NaCl absorption in the mTALH depends on a secondary active transport process: NaCl entry across luminal membranes is a coupled process of indeterminate stoichiometry that is driven by the transmembrane electrochemical gradient for Na+, which is maintained by Na+-K+-ATPase. Finally, the data demonstrate that the mTALH is electrically leaky whether measured electrically, 11 omega . cm2, or isotopically, 50 omega . cm2, but essentially water impermeable; and that the mTALH is perm-selective for Na+ with respect to Cl-. The disparity between electrical resistances measured directly with respect to those calculated from tracer fluxes, together with the hybrid characteristics of mTALH junctional complexes (leaky to Na+ and Cl-; tight to water), may be reconciled by assuming that mTALH junctional complexes contain passive ion permeation pathways composed of narrow channels through which ions pass in single-file fashion.

Poly(methyl methacrylate) membranes

AbstractUniform and symmetric membranes were formed from poly(methyl methacrylate) (PMMA) by making use of the stereocomplex phenomenon which characteristically occurs in the solution of a mixture of isotactic PMMA and syndiotactic PMMA. The water permeability of the membrane was very high compared to a commercially available cellulosic membrane, whereas their NaCl permeabilities were the same. The permeabilities of the membranes are explained by a simple capillary model. By varying the tacticity of the polymer it was found that the finest membrane structure is formed at the isotactic polymer ratio of ca. 30%. This shows the close relationship between complex formation and membrane permeability.

Permeabilities of coagulated cellulose acetate dialysis membranes

AbstractThe diffusive flux of NaCl and the hydraulic flux of pure water through coagulated cellulose acetate membranes are examined. Coagulated cellulose acetate membranes (without densification by heat treatment or drying) possess higher permeability than what may be expected from the permeabilities of the dry polymer. Their overall hydraulic permeability (ultrafiltration rate of water) is greatly dependent upon the membrane casting conditions and the resulting asymmetry of the membrane. On the other hand, the asymmetry of a membrane does not play as great a role in the diffusive permeability of a solute. With homogeneous membranes, higher diffusive flux is always accompanied by higher hydraulic permeability. With asymmetric membranes, this is not always true. The diffusive permeability of NaCl and the hydraulic permeability of water through coagulated cellulose acetate membranes can be controlled nearly independently. Consequently, high diffusive (NaCl) permeability with low hydraulic water permeability and vice versa can be obtained by varying the casting conditions and also by partially saponifying the denser portion of the membrane.