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Guanylin (GN) and uroguanylin (UGN) are low-molecular-weight peptide hormones produced mainly in the intestinal mucosa in response to oral salt load. GN and UGN (guanylin peptides) induce secretion of electrolytes and water in both intestine and kidney. Thought to act as “intestinal natriuretic factors”, GN and UGN modulate renal salt secretion by both endocrine mechanisms (linking the digestive system and kidney) and paracrine/autocrine (intrarenal) mechanisms. The cellular function of GN and UGN in intestine and proximal tubule is mediated by guanylyl cyclase C (GC-C)-, cGMP-, and G protein-dependent pathways, whereas, in principal cells of the cortical collecting duct (CCD), these peptide hormones act via GC-C-independent signaling through phospholipase A2 (PLA2). The Cl-/HCO-3 exchanger pendrin (SLC26A4), encoded by the PDS gene, is expressed in non-α intercalated cells of the CCD. Pendrin is essential for CCD bicarbonate secretion and is also involved in NaCl balance and blood pressure regulation. Our recent studies have provided evidence that pendrin-mediated anion exchange in the CCD is regulated at the transcriptional level by UGN. UGN exerts an inhibitory effect on the pendrin gene promoter likely via heat shock factor 1 (HSF1) action at a defined heat shock element (HSE) site. Recent studies have unraveled novel roles for guanylin peptides in several organ systems including involvement in appetite regulation, olfactory function, cell proliferation and differentiation, inflammation, and reproductive function. Both the guanylin system and pendrin have also been implicated in airway function. Future molecular research into the receptors and signal transduction pathways involved in the action of guanylin peptides and the pendrin anion exchanger in the kidney and other organs, and into the links between them, may facilitate discovery of new therapies for hypertension, heart failure, hepatic failure and other fluid retention syndromes, as well as for diverse diseases such as obesity, asthma, and cancer.

Background /Aim: Genistein, the most active isoflavone found primarily in soybeans, alters ion transport functions in intestinal and airway epithelia. The present study aims to investigate the acute effects and mechanisms of action of genistein in immortalized porcine endometrial epithelial cells. Methods: Ussing chamber technique was used for transepithelial electrical measurements. Results: Genistein increased short-circuit currents (Isc) which were inhibited by glibenclamide, NPPB, CFTRinh-172, DIDS or bumetanide, but not amiloride. In experiments with amphotericin B-permeabilized monolayers, genistein activated the apical Cl- current and barium-sensitive basolateral K+ current while inhibiting the apical K+ current. Genistein failed to increase the Isc in the presence of forskolin or IBMX, but did increase the Isc in UTP. Pretreatment with genistein also abolished the increase in the Isc when induced by forskolin, IBMX or UTP. However, Ca2+-chelating BAPTA-AM did not affect the genistein-induced increase in the Isc. The genistein-stimulated Isc was reduced by tyrosine kinase inhibitors, tyrphostin A23 or AG490. However, vanadate, a tyrosine phosphatase inhibitor, failed to inhibit the genistein response. Estrogen receptor antagonist ICI182,780 did not alter the genistein's action. Conclusion: The soy isoflavone, genistein, stimulates Cl- secretion in endometrial epithelial cells possibly via a direct activation of CFTR which appears to be modulated through a tyrosine kinase-dependent pathway. The present findings may be of benefit for the therapeutic application of genistein in the treatment of electrolyte transport disorders in the epithelia.

The accumulation of high concentrations of chloride (Cl-) in leaves can adversely affect plant growth. When comparing different varieties of the same Cl- sensitive plant species those that exclude relatively more Cl- from their shoots tend to perform better under saline conditions; however, the molecular mechanisms involved in maintaining low shoot Cl- remain largely undefined. Recently, it was shown that the NRT1/PTR Family 2.4 protein (NPF2.4) loads Cl- into the root xylem, which affects the accumulation of Cl- in Arabidopsis shoots. Here we characterize NPF2.5, which is the closest homolog to NPF2.4 sharing 83.2% identity at the amino acid level. NPF2.5 is predominantly expressed in root cortical cells and its transcription is induced by salt. Functional characterisation of NPF2.5 via its heterologous expression in yeast (Saccharomyces cerevisiae) and Xenopus laevis oocytes indicated that NPF2.5 is likely to encode a Cl- permeable transporter. Arabidopsis npf2.5 T-DNA knockout mutant plants exhibited a significantly lower Cl- efflux from roots, and a greater Cl- accumulation in shoots compared to salt-treated Col-0 wild-type plants. At the same time, NO-3 content in the shoot remained unaffected. Accumulation of Cl- in the shoot increased following (1) amiRNA-induced knockdown of NPF2.5 transcript abundance in the root, and (2) constitutive over-expression of NPF2.5. We suggest that both these findings are consistent with a role for NPF2.5 in modulating Cl- transport. Based on these results, we propose that NPF2.5 functions as a pathway for Cl- efflux from the root, contributing to exclusion of Cl- from the shoot of Arabidopsis. [ABSTRACT FROM AUTHOR]

• Carbonation accelerates the deterioration of AAFA under chloride-sulfate attack condition. • The deterioration of AAFS caused by carbonation was less serious compared with AAS. • Sulfate coupling reduces the chloride transport of AAFS suffered chloride-carbonation attack. • The gap between AAFA and AAS in chloride transport became smaller with exposure time. • AAFS shows the best long term performance exposed to chloride-sulfate-carbonation attack. The chloride transportation in alkali-activated fly ash (AAFA), alkali-activated slag (AAS) and alkali-activated fly ash/slag (AAFS) concrete exposed to the environments of single chloride and combined of chloride, sulfate and carbonation were investigated. The iodide migration, chloride diffusion and capillary absorption tests were carried out before and after exposure, as well as the analysis of their microstructure and compositions. It was found that the initial chloride transport of AAFA concrete was the highest but decreased gradually with the increase of exposure period. For AAFA and AAFS specimens with a relatively lower strength, chloride and sulfate salt crystallization led to the surface spalling and strength reduction. The coupling of carbonation would further accelerate the deterioration of AAFA, but the inhibitory effect was acted for AAFS specimen. Although the appearance of AAS specimens had little change under various aggressive environments, carbonation led to the decalcification of C-(A)-S H gels and deterioration of pore structure, both the porosity and the harmful 10–50 nm pores content of the specimens were higher compared with that before exposure, and their chloride transport increased with time. However, the deterioration of AAFS specimens resulted from carbonation was less serious, due to the formation of C-(N)-A S H gels with a higher degree of cross-linking and polymerization, thereby it had the best long term performance under the combined environment of chloride, sulfate and carbonation. [ABSTRACT FROM AUTHOR]

• The proper content of supplementary cementitious materials (SCMs) can improve the compressive strength and chloride resistance of RAC. • The three kinds of SCMs can improve the pore structure of ITZs, thus improving the compactness of ITZ. • The SCMs can increase the microhardness of ITZ and decrease the width of ITZ. • The best dosages of fly ash, slag powder and silica fume are 20%, 30% and 6%, respectively. Among the three SCMs, silica fume demonstrates the best properties improvement. The poor performance of recycled aggregate concrete (RAC) limits its application on wide filed. This paper attempted to study the influence of fly ash (FA), slag powder (SP) and silica fume (SF) on the performance of RAC from a microscopic point of view. The compressive strength and chloride resistance were evaluated when FA, SP and SF were used. Then the evolution of ITZ performance with different admixtures was observed by backscattering scanning electron (BSE) microscopy image, Mercury intrusion porosimetry (MIP), microhardness and so forth. Results indicate that, (1) the supplementary cementitious materials (SCMs) can improve the compressive strength and chloride penetration resistance of RAC, with a certain dosage range for different SCMs; (2) the SCMs can refine the pore structure of ITZs for RAC, increase the microhardness and modify the phases around ITZs; (3) the three SCMs both fill the cement paste voids and promote the compactness of ITZ structure by reacting with calcium hydroxide to generate C S H gels, which in turn enhance the macroscopic performance of RAC. The results of this research can provide a meaningful reference for further study of SCMs to improve the ITZs structure of RAC. [ABSTRACT FROM AUTHOR]

Diffusion has been systematically described as the main mechanism of chloride transport in reinforced concrete (RC) structure, especially when the concrete is in a saturated state. However, the single mechanism of diffusion is not able to describe the actual chloride ingress in the nonsaturated concrete. Instead, it is dominated by the interaction of diffusion and convection. With the synergetic effects of various factors taken into account, this study aimed to modify and develop an analytical convection- diffusion coupling model for chloride transport in nonsaturated concrete. The model was verified by simulation of laboratory tests and field measurement. The results of comparison study demonstrate that the analytical model developed in this study is efficient and accurate in predicting the chloride profiles in the nonsaturated concrete. [ABSTRACT FROM AUTHOR]

The two major interfaces separating brain and blood have different primary roles. The choroid plexuses secrete cerebrospinal fluid into the ventricles, accounting for most net fluid entry to the brain. Aquaporin, AQP1, allows water transfer across the apical surface of the choroid epithelium; another protein, perhaps GLUT1, is important on the basolateral surface. Fluid secretion is driven by apical Na+-pumps. K+ secretion occurs via net paracellular influx through relatively leaky tight junctions partially offset by transcellular efflux. The blood-brain barrier lining brain microvasculature, allows passage of O2, CO2, and glucose as required for brain cell metabolism. Because of high resistance tight junctions between microvascular endothelial cells transport of most polar solutes is greatly restricted. Because solute permeability is low, hydrostatic pressure differences cannot account for net fluid movement; however, water permeability is sufficient for fluid secretion with water following net solute transport. The endothelial cells have ion transporters that, if appropriately arranged, could support fluid secretion. Evidence favours a rate smaller than, but not much smaller than, that of the choroid plexuses. At the blood-brain barrier Na+ tracer influx into the brain substantially exceeds any possible net flux. The tracer flux may occur primarily by a paracellular route. The blood-brain barrier is the most important interface for maintaining interstitial fluid (ISF) K+ concentration within tight limits. This is most likely because Na+-pumps vary the rate at which K+ is transported out of ISF in response to small changes in K+ concentration. There is also evidence for functional regulation of K+ transporters with chronic changes in plasma concentration. The blood-brain barrier is also important in regulating HCO3- and pH in ISF: the principles of this regulation are reviewed. Whether the rate of blood-brain barrier HCO3- transport is slow or fast is discussed critically: a slow transport rate comparable to those of other ions is favoured. In metabolic acidosis and alkalosis variations in HCO3- concentration and pH are much smaller in ISF than in plasma whereas in respiratory acidosis variations in pHISF and pHplasma are similar. The key similarities and differences of the two interfaces are summarized. [ABSTRACT FROM AUTHOR]

• Set relationship between convection depth, peak concentration and dry-wet ratio. • Raise freeze–thaw damage impact coefficients to quantify effects on convection zone. • Propose prediction equation of convection depth considering freezing-thawing effect. • Establish chloride transport model with the coupling effects of D/W and FT damage. In marine environment, dry-wet ratio (D/W) in the dry-wet cycling zone of coastal structures and freeze–thaw (FT) damage can both affect the chloride transport characteristics in concrete. In this paper, FT cycling tests of concrete specimens were conducted by the FT cycles testing machine to establish the relationship between the number of FT cycles and FT damage. Then, the chloride natural diffusion tests of concrete specimens with different FT damage under the dry-wet cycling zone were carried out to investigate the chloride transport law considering the coupling effects of D/W and FT damage on the condition of the dry-wet cycling period = 24 h. Under the influence of dry-wet cycles, there is a convection zone in the transmission of chloride in concrete specimens. Based on the Fick's second law, the convection zone peak concentration, the convection zone depth and the apparent chloride diffusion coefficient considering the coupling effects of D/W and FT damage were determined by fitting the chloride concentration distributions at various exposure time. The results show that the effect laws of D/W on unfrozen and frozen concrete specimens are basically the same. The convection zone peak concentration, the convection zone depth and the apparent chloride diffusion coefficient increase with the increase of FT damage in concrete specimens. The influences of FT damage on the convection zone peak concentration, the convection zone depth and the apparent chloride diffusion coefficient were quantified by introducing the impact coefficients of FT damage. Finally, a prediction model of chloride transport in concrete considering the coupling effects of D/W and FT damage was proposed, and the accuracy and reasonability of the prediction model were validated by comparing the predictive results of the model and the measured values of the tests. [ABSTRACT FROM AUTHOR]

Progressive familial intrahepatic cholestasis type 1 (PFIC1) is caused by mutations in the gene encoding the phospholipid flippase ATP8B1. Apart from severe cholestatic liver disease, many PFIC1 patients develop extrahepatic symptoms characteristic of cystic fibrosis (CF), such as pulmonary infection, sweat gland dysfunction and failure to thrive. CF is caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR), a chloride channel essential for epithelial fluid transport. Previously it was shown that CFTR transcript levels were strongly reduced in livers of PFIC1 patients. Here we have investigated the hypothesis that ATP8B1 is important for proper CFTR expression and function. We analyzed CFTR expression in ATP8B1-depleted intestinal and pulmonary epithelial cell lines and assessed CFTR function by measuring short-circuit currents across transwell-grown ATP8B1-depleted intestinal T84 cells and by a genetically-encoded fluorescent chloride sensor. In addition, we studied CFTR surface expression upon induction of CFTR transcription. We show that CFTR protein levels are strongly reduced in the apical membrane of human ATP8B1-depleted intestinal and pulmonary epithelial cell lines, a phenotype that coincided with reduced CFTR activity. Apical membrane insertion upon induction of ectopically-expressed CFTR was strongly impaired in ATP8B1-depleted cells. We conclude that ATP8B1 is essential for correct apical localization of CFTR in human intestinal and pulmonary epithelial cells, and that impaired CFTR localization underlies some of the extrahepatic phenotypes observed in ATP8B1 deficiency. [ABSTRACT FROM AUTHOR]

Impaired neuronal inhibition has long been associated with the increased probability of seizure occurrence and heightened seizure severity. Fast synaptic inhibition in the brain is primarily mediated by the type A γ-aminobutyric acid receptors (GABA A Rs), ligand-gated ion channels that can mediate Cl − influx resulting in membrane hyperpolarization and the restriction of neuronal firing. In most adult brain neurons, the K + /Cl − co-transporter-2 (KCC2) establishes hyperpolarizing GABAergic inhibition by maintaining low [Cl − ] i . In this study, we sought to understand how decreased KCC2 transport function affects seizure event severity. We impaired KCC2 transport in the 0-Mg 2+ ACSF and 4-aminopyridine in vitro models of epileptiform activity in acute mouse brain slices. Experiments with the selective KCC2 inhibitor VU0463271 demonstrated that reduced KCC2 transport increased the duration of SLEs, resulting in non-terminating discharges of clonic-like activity. We also investigated slices obtained from the KCC2-Ser940Ala (S940A) point-mutant mouse, which has a mutation at a known functional phosphorylation site causing behavioral and cellular deficits under hyperexcitable conditions. We recorded from the entorhinal cortex of S940A mouse brain slices in both 0-Mg 2+ ACSF and 4-aminopyridine, and demonstrated that loss of the S940 residue increased the susceptibility of continuous clonic-like discharges, an in vitro form of status epilepticus. Our experiments revealed KCC2 transport activity is a critical factor in seizure event duration and mechanisms of termination. Our results highlight the need for therapeutic strategies that potentiate KCC2 transport function in order to decrease seizure event severity and prevent the development of status epilepticus. [ABSTRACT FROM AUTHOR]

Chloride-induced corrosion of steel in reinforced concrete structures is one of the main problems affecting their durability, but most previous research projects and case studies have focused on concretes without cracks or not subjected to any structural load. Although it has been recognised that structural cracks do influence the chloride transport and chloride induced corrosion in reinforced concrete structures, there is little published work on the influence of micro-cracks due to service loads on these properties. Therefore the effect of micro-cracks caused by loading on chloride transport into concrete was studied. Four different stress levels (0%, 25%, 50% and 75% of the stress at ultimate load – f u ) were applied to 100 mm diameter concrete discs and chloride migration was measured using a bespoke test setup based on the NT BUILD 492 test. The effects of replacing Portland cement CEMI by ground granulated blast-furnace slag (GGBS), pulverised fuel ash (PFA) and silica fume (SF) on chloride transport in concrete under sustained loading were studied. The results have indicated that chloride migration coefficients changed little when the stress level was below 50% of the f u ; however, it is desirable to keep concrete stress less than 25% f u if this is practical. The effect of removing the load on the change of chloride migration coefficient was also studied. A recovery of around 50% of the increased chloride migration coefficient was found in the case of concretes subjected to 75% of the f u when the load was removed. [ABSTRACT FROM AUTHOR]

Concrete cracking usually is an unavoidable phenomenon in reinforced concrete (RC) structures and has a significant effect on chloride diffusion and thus the deterioration of the structures. However, actual concrete cracks have complicated characteristics, and the mechanisms in which they influence the chloride penetration have not yet been well clarified. This study presents a careful quantification of the geometrical parameters of actual concrete cracks, including density, orientation, tortuosity and width, and explores their correlation with the chloride diffusion properties of concrete. Uni-axial compression tests were conducted on concrete specimens to create various extents of cracking severity. Afterwards, a non-steady state migration method was employed to evaluate the diffusivity of sound and cracked concretes. The geometry parameters of concrete cracks were quantified by an image analysis technique after the migration tests. The test results suggest a linear relationship between the crack tortuosity and the degree of crack orientation. In addition, chloride diffusion into concrete depends greatly on the crack density and crack tortuosity in addition to the crack width. In particular, the crack tortuosity is a critical factor influencing chloride penetration when the crack width ranges from 150 to 370 μm. Considering the crack tortuosity and orientation, the effective crack width and effective crack density are proposed as correlated with the chloride diffusivity of cracked concrete. [ABSTRACT FROM AUTHOR]

Angiotensin II (ANG II) is secreted by the proximal tubule resulting in a luminal concentration that is 100- to 1,000-fold greater than that in the blood. Luminal ANG II has been shown to stimulate sodium transport in the proximal tubule and distal nephron. Surprisingly, luminal ANG II inhibits NaCl transport in the medullary thick ascending limb (mTAL), a nephron segment responsible for a significant amount of NaCl absorption from the glomerular ultrafiltrate. We confirmed that addition of 10-8 M ANG II to the lumen inhibited mTAL chloride transport (220 ± 19 to 165 ± 25 pmol·mm-1·min-1, P < 0.01) and examined whether an interaction with basolateral norepinephrine existed to simulate the in vivo condition of an innervated tubule. We found that in the presence of a 10-6 Mnorepinephrine bath, luminal ANG II stimulated mTAL chloride transport from 298 ± 18 to 364 ± 42 pmol·mm-1·min-1 (P < 0.05). Stimulation of chloride transport by luminal ANG II was also observed with 10-3 M bath dibutyryl cAMP in the bathing solution and bath isoproterenol. A bath of 10-5 H-89 blocked the stimulation of chloride transport by norepinephrine and prevented the effect of luminal ANG II to either stimulate or inhibit chloride transport. Bath phentolamine, an α-adrenergic agonist, also prevented the decrease in mTAL chloride transport by luminal ANG II. Thus luminal ANG II increases chloride transport with basolateral norepinephrine; an effect likely mediated by stimulation of cAMP. Alpha-1 adrenergic stimulation prevents the inhibition of chloride transport by luminal ANG II. [ABSTRACT FROM AUTHOR]

To clarify the mechanism of chloride penetration into concrete subjected to drying-wetting cycles, two kinds of concrete, ordinary portland cement concrete and fly ash (FA) concrete, were tested in a cyclic NaCl solution to show the influence of mix proportion, period ratio of drying to wetting, and exposure time. Based on the experimental profiles of free chloride concentration obtained after 30 and 60 weeks, it was found that the depth of convection zone varied from 6 to 15 mm and increased in duration when the air-drying period in one cycle was prolonged or the exposure time increased. Through a regression analysis of chloride profiles located in the inner part of the concrete beyond the advection zone, it was verified that diffusion was the dominant mechanism of chloride transport and could be well fitted with the proposed modified diffusion model taking into account the influence of convection depth. Finally, the time-dependent chloride diffusion coefficient DCl was calculated on the basis of the apparent chloride diffusion coefficient Dapp and the obtained time exponent m. The effect of FA content on DCl was also examined. [ABSTRACT FROM AUTHOR]

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Cattle feeding in feedlot pens produces large amounts of manure and animal urine. Manure solutions resulting from surface runoff are composed of numerous chemical constituents whose leaching causes salinization of the soil profile. There is a relatively large number of studies on preferential flow characterization and modeling in clayed soils. However, research on water flow and solute transport derived from cattle feeding operations in fine-textured soils under naturally occurring precipitation events is less frequent. A field monitoring and modeling investigation was conducted at two plots on a fine-textured soil near a feedlot pen in Argentina to assess the potential of solute leaching into the soil profile. Soil pressure head and chloride concentration of the soil solution were used in combination with HYDRUS-1D numerical model to simulate water flow and chloride transport resorting to the concept of mobile/immobile—MIM water for solute transport. Pressure head sensors located at different depths registered a rapid response to precipitation suggesting the occurrence of preferential flow-paths for infiltrating water. Cracks and small fissures were documented at the field site where the % silt and % clay combined is around 94%. Chloride content increased with depth for various soil pressure head conditions, although a dilution process was observed as precipitation increased. The MIM approach improved numerical results at one of the tested sites where the development of cracks and macropores is likely, obtaining a more dynamic response in comparison with the advection–dispersion equation. [ABSTRACT FROM AUTHOR]

Development of the human civilization leads to the pollution of environment. One of the contamination which are a real threat to soil and groundwater are leachates from landfills. In this paper the solute transport through soil was considered. For this purpose, the laboratory column tests of chlorides tracer and leachates transport on two soil samples have been carried out. Furthermore, the electrical resistivity method was applied as auxiliary tool to follow the movements of solute through the soil column what allowed to compare between the results obtained with column test method and electrical resistivity measurements. Breakthrough curves obtained by conductivity and resistivity methods represents similar trends which leads to the conclusion about the suitability of electrical resistivity methods for contamination transport monitoring in soil-water systems. [ABSTRACT FROM AUTHOR]

Cl − transport in animal cells has fundamental physiological roles and it is mediated by a variety of protein families, one of them being the CLC family of ion channels and transporters. Besides their physiological relevance, CLC proteins show peculiar biophysical properties. This review will focus on a member of the CLC protein family, the endosomal Cl − /H + antiporter ClC-5. ClC-5 mutations cause Dent's disease, a renal syndrome due to defective protein reabsorption in the proximal tubule. This established the critical function of ClC-5 for endocytosis. However, our understanding of ClC-5's molecular role in endosomes and of its biophysical properties has proved elusive in spite of important progress achieved in the last two decades. Early models in which ClC-5 would provide a shunt conductance to enable efficient endosomal acidification conflicted with the antiport activity of ClC-5 that has more recently emerged. Currently, the physiological role of ClC-5 is hotly debated and its biophysical properties are still not fully understood. [ABSTRACT FROM AUTHOR]

Here we present a theoretical interpretation of high-frequency, high-quality tracer time series from the Hafren catchment at Plynlimon in mid-Wales. We make use of the formulation of transport by travel time distributions to model chloride transport originating from atmospheric deposition and compute catchment-scale travel time distributions. The relevance of the approach lies in the explanatory power of the chosen tools, particularly to highlight hydrologic processes otherwise clouded by the integrated nature of the measured outflux signal. The analysis reveals the key role of residual storages that are poorly visible in the hydrological response, but are shown to strongly affect water quality dynamics. A significant accuracy in reproducing data is shown by our calibrated model. A detailed representation of catchment-scale travel time distributions has been derived, including the time evolution of the overall dispersion processes (which can be expressed in terms of time-varying storage sampling functions). Mean computed travel times span a broad range of values (from 80 to 800 days) depending on the catchment state. Results also suggest that, in the average, discharge waters are younger than storage water. The model proves able to capture high-frequency fluctuations in the measured chloride concentrations, which are broadly explained by the sharp transition between groundwaters and faster flows originating from topsoil layers. [ABSTRACT FROM AUTHOR]

The simultaneous transport of water and chloride in concrete has been modelled. The water transport is described with a concentration dependent diffusion coefficient. The chloride transport is modelled with a convective part, caused by the water transport, and a diffusive part, caused by the chloride concentration gradient in the pore water. Because the water velocity depends on the pore radius, the chloride transport is a complex pore radius dependent process. Modelling this process leads to an expression for the dispersion coefficient, for the chloride diffusion. The model equations are applied on concrete with a yearly variation of the surface water concentration. A few different boundary conditions for the chloride transport are described. The water distribution is almost homogeneous over the samples. The chloride concentration at the surface can rise considerably, when water leaves the concrete sample, while chloride stays behind. Crystallization and a few other possible model extensions are discussed. [ABSTRACT FROM AUTHOR]

The kidney continuously adapts daily renal excretion of NaCl to match dietary intakes in order to maintain the NaCl content of the body, and keep vascular volume constant. Any situation that leads to NaCl retention favors a rise in blood pressure. The aldosterone-sensitive distal nephron, which contains two main types of cells, principal (PC) and intercalated (IC) cells, is an important site for the final regulation of urinary Na excretion. Research over the past 20 years established a paradigm in which PCs are the exclusive site of Na absorption while ICs are solely dedicated to acid-base transport. Recent studies have revealed the unexpected importance of ICs for NaCl reabsorption. Here, we review the mechanisms of Na and Cl transport in the aldosterone-sensitive distal nephron, with emphasis on the role of ICs in maintaining NaCl balance and normal blood pressure. [ABSTRACT FROM AUTHOR]

The growing interest in the study of membraneactive ion (in particular, anion) transporters motivates the investigation of the mechanisms that underlie the transport process. The interest of the scientific community in this area is largely due to the great importance of transmembrane ion-transport phenomena in many diseases. In this paper we investigated the role of calix[6]arene-based pseudorotaxanes and rotaxanes on transmembrane transport of ions across the bilayer of liposomes composed of 1-palmitoyl-2-oleoylsn- glycero-3-phosphocholine (POPC; diameter 100 nm). We evaluated the effect of these interlocked systems on the properties of the bilayer and on membrane permeability towards chloride ions and 5(6)-carboxyfluorescein. These findings may pave the way for the construction of new generations of pharmacological systems regulating the transport of chloride ions. [ABSTRACT FROM AUTHOR]