Role Of Salts Research Articles

Spermidine mitigates salt stress in grapevine with alterations in physicochemical properties and nutrient composition

AbstractBackgroundPolyamines are plant growth regulators that exert a pivotal role in salt tolerance.AimsThis research focused on investigating the effect of spermidine on morphological and physicochemical characteristics and ion accumulation of two grapevine cultivars under NaCl stress.MethodsA greenhouse experiment was conducted with three factors, including two grapevine cultivars (Vitis vinifera L. cv. Bidaneh‐Sefid and cv. Siah‐Sardasht), four levels of NaCl (together with the nutrient solution, including 0 [control], 20, 40, and 80 mM), and four spermidine levels ([foliar spray], 0 [control], 0.25, 0.5, and 1 mM). The experiment was performed in a factorial trial in accordance with a randomized complete design with three replicates.ResultsVegetative growth indices, including leaf number, fresh and dry weight of shoot, and root, were decreased by NaCl treatments. The application of spermidine positively reduced the effects of NaCl on morphological characteristics. Moreover, NaCl and/or spermidine significantly (p ≤ 0.05) improved antioxidant enzyme activities associated with rising total protein accumulation. NaCl stress significantly decreased ion percentage (calcium, magnesium, phosphate, potassium, iron, and zinc) in the leaves of both cultivars. Based on the results, increasing salinity levels significantly boosted plant Na+ and Cl− percentage, along with increased membrane permeability and malondialdehyde (MDA) concentration. Interestingly, cv. Bidaneh‐Sefid leaves accumulated less Na+ and Cl− compared to the other cultivar. On the other hand, applying spermidine reduced the levels of Na+ and Cl− in both cultivars, and this reduction was associated with a decrease in membrane permeability and MDA concentration.ConclusionsThe findings confirmed the role of spermidine in reducing the negative effects of NaCl, although more investigations with different grapevine cultivars under NaCl stress are required.

Genome-wide identification of WRKY transcription factors in Casuarina equisetifolia and the function analysis of CeqWRKY11 in response to NaCl/NaHCO3 stresses

BackgroundCasuarina equisetifolia (C. equisetifolia) is a woody species with many excellent features. It has natural resistance against drought, salt and saline-alkali stresses. WRKY transcription factors (TFs) play significant roles in plant response to abiotic stresses, therefore, molecular characterization of WRKY gene family under abiotic stresses holds great significance for improvement of forest trees through molecular biological tools. At present, WRKY TFs from C. equisetifolia have not been thoroughly studied with respect to their role in salt and saline-alkali stresses response. The current study was conducted to bridge the same knowledge gap.ResultsA total of 64 WRKYs were identified in C. equisetifolia and divided into three major groups i.e. group I, II and III, consisting of 10, 42 and 12 WRKY members, respectively. The WRKY members in group II were further divided into 5 subgroups according to their homology with Arabidopsis counterparts. WRKYs belonging to the same group exhibited higher similarities in gene structure and the presence of conserved motifs. Promoter analysis data showed the presence of various response elements, especially those related to hormone signaling and abiotic stresses, such as ABRE (ABA), TGACG (MeJA), W-box ((C/T) TGAC (T/C)) and TC-rich motif. Tissue specific expression data showed that CeqWRKYs were mainly expressed in root under normal growth conditions. Furthermore, most of the CeqWRKYs were up-regulated by NaCl and NaHCO3 stresses with few of WRKYs showing early responsiveness to both stresses while few others exhibiting late response. Although the expressions of CeqWRKYs were also induced by cold stress, the response was delayed compared with other stresses. Transgenic C. equisetifolia plants overexpressing CeqWRKY11 displayed lower electrolyte leakage, higher chlorophyll content, and enhanced tolerance to both stresses. The higher expression of abiotic stress related genes, especially CeqHKT1 and CeqPOD7, in overexpression lines points to the maintenance of optimum Na+/K+ ratio, and ROS scavenging as possible key molecular mechanisms underlying salt stress tolerance.ConclusionsOur results show that CeqWRKYs might be key regulators of NaCl and NaHCO3 stresses response in C. equisetifolia. In addition, positive correlation of CeqWRKY11 expression with increased stress tolerance in C. equisetifolia encourages further research on other WRKY family members through functional genomic tools. The best candidates could be incorporated in other woody plant species for improving stress tolerance.

NRF2 in kidney physiology and disease.

The role of NRF2 in kidney biology has received considerable interest over the past decade. NRF2 transcriptionally controls genes responsible for cellular protection against oxidative and electrophilic stress and has anti-inflammatory functions. NRF2 is expressed throughout the kidney and plays a role in salt and water handling. In disease, animal studies show that NRF2 protects against tubulointerstitial damage and reduces interstitial fibrosis and tubular atrophy, and may slow progression of polycystic kidney disease. However, the role of NRF2 in proteinuric glomerular diseases is controversial. Although the NRF2 inducer, bardoxolone methyl (CDDO-Me), increases glomerular filtration rate in humans, it has not been shown to slow disease progression in diabetic kidney disease and Alport syndrome. Furthermore, bardoxolone methyl was associated with negative effects on fluid retention, proteinuria, and blood pressure. Several animal studies replicate findings of worsened proteinuria and a more rapid progression of kidney disease, although considerable controversy exists. It is clear that further study is needed to better understand the effects of NRF2 in the kidney. This review summarizes the available data to clarify the promise and risks associated with targeting NRF2 activity in the kidney.

Along-strike variations of structural style in the external Western Alps (France): Review, insights from analogue models and the role of salt

The European Alps result from the closure of a former Triassic to Cretaceous rifting system in which significative accumulation of Upper Triassic salt deposited. The thickness and spatial distribution of these salts had a major impact on the morphology and dynamic of the Alpine orogen all over the Western Alps. Following a bibliographical review, four regional cross-sections are revisited over the External Western Alps to emphasise along-strike variations of the orogenic wedge influenced by the presence or absence of Triassic salts. Each section is then compared with analogue models to examine the controlling factors explaining the structural styles variations. In the Northern Subalpine Chains, the absence of salt favoured a frictional decollement which promoted a narrow and thick orogenic wedge in the Bornes, Chartreuse, and Vercors massifs. Discrepancies in the spacing between the thrusts and the number of folds were however influenced by the thickness of incompetent layers in the sedimentary column. In the Jura and the SW Alps, the occurrence of Triassic salts promoted a viscous decollement and thus a wide and relatively thin orogenic wedge. However, in the SW Alps, thicker salt deposits allowed the development of pre-orogenic salt structures. These later constituted vertical heterogeneities having exerted a strong structural inheritance during the following compression, by accommodating a substantial part of the Alpine shortening, in squeezed diapirs especially. Triassic salt remobilization during the orogeny also locally promoted the development of syn-orogenic minibasins. This review highlights the significant role played by Triassic salt in shaping the Western Alps, and paves the way for possible new interpretations of the dynamics of the Alps regarding the exhumation of crystalline basement blocks, or new structural interpretations of Alpine domains, such as the Vocontian Domain.

Comparative Study of Deterioration in Built Heritage in a Coastal Area: Barbanza Peninsula (Galicia, NW Spain)

The Barbanza Peninsula (Galicia, NW Spain) is located on the west coast of Galicia. It is a narrow tongue of terrain with an area of 416 km2 and a high altitudinal gradient, with the top having a maximum height of more than 600 m at a distance of less than 5 Km from the sea. As a result of this, there is a significant rainfall gradient (from 900 to more than 3300 mm per year). In the peninsula, there are valuable historical buildings built with granite rock that show variable decay patterns. In this work, we have considered 14 of them, located in several parts of the peninsula, and we have studied their deterioration patterns. Some of them are close to the sea, with sea salt being a possible cause of decay, while for those located far from the sea, the high humidity and rainfall can be the most important cause of decay. A macroscopic study was carried out to determine the deterioration patterns. We have also analyzed the possible role of salts in the decay by using X-ray fluorescence as a screening technique to assess the presence of salts and the possible correlation of salts with the distance to the sea and using scanning electron microscopy to directly identify salts in some of the buildings. The most frequently reported decay is due to lichen growth (biological colonization). Depending on the proximity to the coast, the study area was divided into two zones: zone 1, closer to the sea (<1 km), with an important influence of sea salts and wind, and zone 2, further from the sea, with higher altitudes (center of the peninsula) and important rainfall, humidity, and therefore, biological colonization of stone surfaces. Crusts (to a lesser degree, because it is a mainly rural area) are more frequent in zone 1, but the state of conservation of stone in zone 1 is better than that in zone 2, possibly due to the concentration of urban centers in this zone and more interventions for cleaning stone surfaces. Finally, although we did not observe clear patterns in the appearance of salts in the buildings in agreement with the distance to the sea, we observed different patterns of salts in two of the buildings, one in each zone, which clearly show that, to some extent, salts are involved in decay.

Phylogeny of PmCCD Gene Family and Expression Analysis of Flower Coloration and Stress Response in Prunus mume.

The CCD gene family plays a crucial role in the cleavage of carotenoids, converting them into apocarotenoids. This process not only impacts the physiology and development of plants but also enhances their tolerance toward different stresses. However, the character of the PmCCD gene family and its role in ornamental woody Prunus mume remain unclear. Here, ten non-redundant PmCCD genes were identified from the P. mume genome, and their physicochemical characteristics were predicted. According to the phylogenetic tree, PmCCD proteins were classified into six subfamilies: CCD1, CCD4, CCD7, CCD8, NCED and CCD-like. The same subfamily possessed similar gene structural patterns and numbers of conserved motifs. Ten PmCCD genes were concentrated on three chromosomes. PmCCD genes exhibited interspecific collinearity with P. armeniaca and P. persica. Additionally, PmCCD genes had obvious specificity in different tissues and varieties. Compared with white-flowered 'ZLE', PmCCD1 and PmCCD4 genes were low-expressed in 'HJH' with yellow petals, which suggested PmCCD1 and PmCCD4 might be related to the formation of yellow flowers in P. mume. Nine PmCCD genes could respond to NaCl or PEG treatments. These genes might play a crucial role in salt and drought resistance in P. mume. Moreover, PmVAR3 and PmSAT3/5 interacted with PmCCD4 protein in yeast and tobacco leaf cells. This study laid a foundation for exploring the role of the PmCCD gene family in flower coloration and stress response in P. mume.

Role of salts in fire extinguishing performance of aqueous film-forming foam (AFFF)

The active ingredients for aqueous film-forming foam (AFFF) are supplied as a concentrate, and the water used to dilute AFFF concentrates generally come from water sources around the fire site including seawater and river water. However, the effects of salt in water on fire-extinguishing performance of AFFF remain unclear. In this paper, we investigated the relationship between the interfacial properties, foam stability, and fire-extinguishing performance of three homemade AFFFs (nonionic AFFFAPG, amphoteric AFFFCAB and anionic AFFFSDS) and four commercial AFFFs. The seawater, firefighting water from different regions of China and deionized water were used to dilute AFFF concentrates. The results showed that AFFFAPG and AFFFCAB had a better performance than AFFFSDS in resisting the negative effects of salts on interfacial properties and foaming ability. In the fire-extinguishing tests, we found that dilution of AFFF with water samples containing high concentrations of Ca2+ and Mg2+ would weaken the fire-extinguishing performance. The traditional indicators characterizing the properties of foam (surface tension, liquid drainage rate, and spreading coefficient) could not explain the trend of fire extinguishing performance. The stability of AFFF in the presence of oil could be used to explain the difference in fire-extinguishing time of AFFF.

The wheat Mitogen Activated Protein Kinase TMPK3 plays a positive role in salt and osmotic stress response

The wheat Mitogen Activated Protein Kinase TMPK3 plays a positive role in salt and osmotic stress response

Molecular Characterization of the Acyl-CoA-Binding Protein Genes Reveals Their Significant Roles in Oil Accumulation and Abiotic Stress Response in Cotton.

Members of the acyl-CoA-binding protein (ACBP) gene family play vital roles in diverse processes related to lipid metabolism, growth and development, and environmental response. Plant ACBP genes have been well-studied in a variety of species including Arabidopsis, soybean, rice and maize. However, the identification and functions of ACBP genes in cotton remain to be elucidated. In this study, a total of 11 GaACBP, 12 GrACBP, 20 GbACBP, and 19 GhACBP genes were identified in the genomes of Gossypium arboreum, Gossypium raimondii, Gossypium babardense, and Gossypium hirsutum, respectively, and grouped into four clades. Forty-nine duplicated gene pairs were identified in Gossypium ACBP genes, and almost all of which have undergone purifying selection during the long evolutionary process. In addition, expression analyses showed that most of the GhACBP genes were highly expressed in the developing embryos. Furthermore, GhACBP1 and GhACBP2 were induced by salt and drought stress based on a real-time quantitative PCR (RT-qPCR) assay, indicating that these genes may play an important role in salt- and drought-stress tolerance. This study will provide a basic resource for further functional analysis of the ACBP gene family in cotton.

Modulation of Lignin and its Implications in Salt, Drought and Temperature Stress Tolerance

Background: Lignins are phenylpropanoid polymers with complex composition and structures and crucial components in plant cell walls. Lignins are biosynthesized from oxidative polymerization of 4-hydroxycinnamyl alcohols, but differ in the degree of methoxylation. Objective: This review makes an endeavour to identify the gaps in our understanding of lignin modulation and gain insights into their relevance to abiotic stress tolerance. Methods: Critical review of the recent literature to understand the regulation of lignin, the major biopolymer involved in a multitude of functions. Results: Lignin contributes to the growth of tissues, and organs that give mechanical protection or lodging resistance and also responds to multiple biotic and abiotic stresses. The quantity and quality of accumulation of lignin is dependent on the type of plant species and abiotic stress. In this review, we briefly discuss the biosynthesis, modulation of lignin by diverse transcription factors and its role in salt, drought and temperature stress tolerance. Conclusion: We need to explore many areas to gain comprehensive knowledge about the secondary cell wall deposition of monolignols, and their transport, leading to lignin accumulation which imparts biotic and abiotic stress tolerance to plants.

Onset of convection from hydrate formation and salt exclusion in marine sands

Short-range diffusion and long-range advection are two endmember mechanisms responsible for transporting methane to locations suitable for hydrate formation in the subsurface. This study introduces a novel transport mechanism in natural porous media: density-driven convection of pore fluids due to hydrate formation and salt exclusion in the pore water. Geologic hydrate systems simulations typically consider the role of salt only as it impacts the equilibrium phase behavior, but have largely ignored its effect on density and mobility impacting fluid flow. In a system sourced with microbially-generated methane, as methane enters a brine-saturated sand from an overlying clay layer, convection is initiated by hydrate formation from methane and water, which excludes salt and thereby increases the salinity of the remaining pore water. As the pore water becomes more saline, the density increases, causing a gravitational instability as the more saline, denser fluid layer overlies a less dense fluid. Fluid parcels are then dragged throughout the layer at a rate as high as 3 cm/yr, which distributes aqueous methane throughout the layer, reaching solubility on a shorter timescale than by diffusion alone. In this study, we examine the factors affecting convection and its ability to transport methane in a layered clay-sand system. We demonstrate the rapid transport of aqueous methane throughout the sand layer with convection compared with diffusion, and how the convective velocity increases with increased hydrate saturation formation rates. The relatively fast rate of convective transport makes convection a viable transport mechanism for supplying deeper sediments with methane generated in shallow regions.

Calcium-dependent protein kinase CDPK16 phosphorylates serine-856 of glutamate receptor-like GLR3.6 protein leading to salt-responsive root growth in Arabidopsis.

Calcium-permeable channels in the plasma membrane play vital roles in plant growth, development, and response to environmental stimuli. Arabidopsis possesses 20 glutamate receptor-like proteins that share similarities with animal ionotropic glutamate receptors and mediate Ca2+ influx in plants. Calcium-dependent protein kinases (CDPKs) phosphorylate serine (Ser)-860 of glutamate receptor-like (GLR)3.7 protein, which interacts with 14-3-3ω and plays an essential role in salt and abscisic acid response in Arabidopsis by modulating Ca2+ signaling. However, the significance of CDPK- mediated phosphorylation status of Ser residues of GLR3.6 with regard to the functioning of GLR3.6 remains to be elucidated. In this study, we performed an in vitro kinase assay using CDPK16 and peptides containing the 14-3-3ω interacting domain of GLR3.6. We showed that Ser861/862 of GLR3.6 are required for the interaction with 14-3-3ω and that Ser856 of GLR3.6 is specifically phosphorylated by CDPK16 but not by CDPK3 and CDPK34. In addition, the expression of GLR3.6 was quickly downregulated by salt stress, and plants of glr3.6 mutants and GLR3.6-overexpression lines presented shorter and longer root lengths, respectively, under normal growth conditions than Col. Overexpression of the GLR3.6-Ser856 to Ala mutation resulted in a less sensitive phenotype in response to salt stress similar to glr3.6. Our results indicated that the Ser861/862 residues of GLR3.6 are required for interaction with 14-3-3ω. Additionally, the phosphorylation status of Ser856 residue of GLR3.6, which is mediated specifically by CDPK16, regulates root growth in normal and salt stress and conditions.

Salt-assisted synthesis of advanced carbon-based materials for energy-related applications

This review provides a comprehensive overview of salt assisted synthesis of carbon based materials based on the role of salts in synthesis systems. Meanwhile, the application in energy related fields is emphasized.

Shale mobility: From salt-like shale flow to fluid mobilization in gravity-driven deformation, the late Albian–Turonian White Pointer Delta (Ceduna Subbasin, Great Bight, Australia)

Large offshore depocenters above a weak detachment level (either salt or shale) can undergo gravity spreading and/or gliding. The gravitational systems (e.g., gliding deltas) are classically composed of an updip domain affected by extensional listric normal faults and a downdip domain affected by toe thrusts. While the role of salt in such systems is a classic tectonic process, the role and mechanical behavior of mobile shale levels in shale-prone gravity-driven systems are increasingly questioned. A three-dimensional seismic data set in the Ceduna Subbasin (Australia) displays the late Albian–Turonian White Pointer Delta (WPD) as having an unusual diversity of shale-cored structures. The early flow of shale resulted in depocenters showing wedges, internal unconformities, and shale diapirs and ridges, while fluidization of shales underneath a significant burial resulted in mud volcanism, secondary radial fault sets, and collapse features beneath the Campanian–Maastrichtian Hammerhead Delta, which lies above the WPD. Massive shale mobilization, together with downdip shortening and distal margin uplift, localized a major thrust in the core of the basin, ending the downward-propagating failure of the WPD. Mobilization of thick shale intervals, either as salt-like flow or mud volcanism, appears to have been a key process in the deformation, which should be considered at large scale for worldwide gravity-driven deformation systems.

Shale mobility: From salt-like shale flow to fluid mobilization in gravity-driven deformation, the late Albian–Turonian White Pointer Delta (Ceduna Subbasin, Great Bight, Australia)

Abstract Large offshore depocenters above a weak detachment level (either salt or shale) can undergo gravity spreading and/or gliding. The gravitational systems (e.g., gliding deltas) are classically composed of an updip domain affected by extensional listric normal faults and a downdip domain affected by toe thrusts. While the role of salt in such systems is a classic tectonic process, the role and mechanical behavior of mobile shale levels in shale-prone gravity-driven systems are increasingly questioned. A three-dimensional seismic data set in the Ceduna Subbasin (Australia) displays the late Albian–Turonian White Pointer Delta (WPD) as having an unusual diversity of shale-cored structures. The early flow of shale resulted in depocenters showing wedges, internal unconformities, and shale diapirs and ridges, while fluidization of shales underneath a significant burial resulted in mud volcanism, secondary radial fault sets, and collapse features beneath the Campanian–Maastrichtian Hammerhead Delta, which lies above the WPD. Massive shale mobilization, together with downdip shortening and distal margin uplift, localized a major thrust in the core of the basin, ending the downward-propagating failure of the WPD. Mobilization of thick shale intervals, either as salt-like flow or mud volcanism, appears to have been a key process in the deformation, which should be considered at large scale for worldwide gravity-driven deformation systems.

Insights into the interaction between lowsal-alkali formulation: Debunking the effect of alkali and lowsal-alkali formulation on the wettability alteration of the quartz substrate

The role of salts in altering the interfacial tension (IFT) and wettability of the rock towards oil recovery is evident through low salinity (lowsal) water flooding. On the other hand, alkali flooding is a well-established method of chemical enhanced oil recovery, which works by reducing the IFT of liquid–liquid system, alters the wettability of rock, and emulsifies the oil–water. Despite having sound knowledge on the applicability of alkali in EOR, the synergistic effect between salts and alkali towards the oil recovery still needs more investigation. In this work, the interaction of salts such as (NaCl and CaCl2) and alkali (NaOH, Na2CO3) on the IFT and wettability of the quartz substrate is investigated. To understand the effect of individual components of crude oil on the IFT and wettability, two different model oils, an aliphatic hydrocarbon (decane), and also actual crude oil from oilfield are employed. It is observed that the lowsal (NaCl)-alkali (NaOH, Na2CO3) formulation effectively reduces the IFT of basic model oil–water and aliphatic-water system than the individual effect of alkali and salts. The lowsal (NaCl)-alkali formulation completely swept the hydrocarbon from the quartz substrate by imparting Marangoni force. Thereby a complete removal of the crude oil droplet from the quartz surface is visually reported for the first time using lowsal (NaCl)-alkali system. These results are further validated by a new approach of Petri dish based static experimental technique which confirms the saponification reaction between acidic and the basic components in the crude oil. Further, the attraction of anionic surfactant (sodium stearate) by cations (Na+) in the NaCl is also validated. We also conclusively show that the increase in contact angle of crude oil and acidic model oil in wettability experiments is primarily due to neutralization reaction and it is not an indicator of oil-wet.

Role of salts on the electrical performance of ceria-based electrolytes: An overview

This work provides an overview on established achievements and debatable findings involving Ca, Gd or Sm-doped ceria-based electrolytes, using Li2CO3, LiNO3 and Na2CO3 as sintering aid or as second phase. The performance of these materials is discussed considering the characteristics of the oxides and of the salts or derived second(ary) phases (e.g., alkali metal oxides and hydroxides, eutectic mixtures), extensively surveyed to identify influential parameters with respect to processing and electrical performance (e.g., melting and boiling points, thermal decomposition, hydrolysis). The analysis of published data highlights the possible contribution of additional charge carriers to the total conductivity, besides oxide-ion vacancies. Claimed bulk and grain boundary conductivity enhancements are deeply discussed, as well as advantages and limitations of impedance spectroscopy as characterization tool. Irrespective of controversial reasons, reports on unusual improvements of grain boundary conductivity sustain the possibility of advanced grain boundary engineering to enhance the performance of these materials.

Role of salts and solvents on the defibrillation of food dye “sunset yellow” induced hen egg white lysozyme amyloid fibrils

Several food dyes are known to induce amyloid fibrillation when interacting with proteins. Here, we studied the role of sunset yellow (SY) in the amyloid fibrillation of hen egg white lysozyme (HEWL) and characterized the changes using spectroscopy techniques. Turbidity results showed that SY dye induces aggregation in HEWL in concentrations dependent manner. The aggregation induced by SY dye is kinetically very fast, no lag phase was detected, and the kinetics process follows an isodesmic kinetics pathway. The SY-dye induce aggregates have cross-β secondary structure confirmed by far-UV CD measurements. The effect of salts and solvents was also seen on SY-induced aggregates. Turbidity, far-UV CD, and kinetics results suggest that certain concentrations of NaCl and (NH4)2SO4 solubilize the SY-induce amyloid fibrils, but (NH4)2SO4 is more effective. Similarly, solvents are also solubilized the SY-induces HEWL amyloid fibrillation but the order of defibrillation is as follows: Isopropanol> ethanol > methanol which signified that isopropanol is more effective than other solvents. The salts and solvents data suggest that the electrostatic, as well as hydrophobic interaction, is responsible for SY-induced amyloid fibrillation. These conformational changes should be examined, more seriously for the purpose of food safety.

Abstract P244: Tubular Sites Of Mtorc2 Inhibition Of Sodium Transport In Dahl Salt-sensitive Rats.

Background: There is evidence that the mTOR signaling pathway plays an important role in salt induced hypertension in the Dahl salt-sensitive (SS) rat via regulation of Na + excretion. PP242 inhibition of mTORC1-2 prevented hypertension in SS rats and intrarenal PP242 produced a 4-fold increase of Na + excretion while selective inhibition of mTORC1 with rapamycin had no effect. The goal of the present study was to identify the renal tubular Na + transporters regulated by the mTORC2 pathway. Methods: Natriuretic effectors of mTORC2 were deduced from the differences of Na + excreted with PP242 treatment beyond that observed by the natriuretic actions of benzamil (B; ENaC inhibitor), furosemide (F; NKCC2 inhibitor), hydrochlorothiazide (H; NCC inhibitor) and in combination (B+F+H). Unanesthetized SS rats were first administered B, F, H or B+F+H (i.p.) and 2 days later with co-administration of PP242 with these same reagents. Rats were studied when fed 0.4% NaCl (LS) and then following 3 weeks of a 4.0% NaCl (HS) diet. The effect of PP242 on ENaC activity in freshly isolated cortical collecting ducts was also examined using cell-attached patch clamp electrophysiology. Results: Urine Na + excretion rates determined at 20 min. intervals over 80 minutes increased nearly 2-fold with administration of PP242 + B, compared to B alone [0.10 + 0.02 vs. 0.04 + 0.01 mmol/100gbw (n=8; P<0.05)] and similarly in the F and H comparisons [F: 0.20 + 0.02 vs. 0.10 + 0.02 mmol/100gbw (n=8; P<0.05); H: 0.05 + 0.01 vs. 0.03 + 0.01 mmol/100gbw (n=8; P=0.06)]. PP242 given in the presence of F+B+H did not further enhance the overall natriuretic response. Rats fed HS showed little enhancement of natriuresis when PP242 was administered with any of the drugs. Minimum changes in K + excretion were observed with PP242 in LS or HS studies. Patch clamp studies found that PP242 reduced ENaC activity through reduction of the open channel probability (Po) in both LS and HS fed rats. Western blot data indicated that PP242 reduced pNCC T53 and phosphorylation of SGK1. Conclusion: Together, these studies found evidence that the natriuretic actions of PP242 are a consequence of inhibitory actions on the ENaC and NCC transporters in the distal nephron segments.

Abstract 099: Role Of Nox-induced Oxidative Stress In Mitochondrial Bioenergetic Dysfunction In The Kidney Cortex And Outer Medulla Of Dahl Salt-sensitive Rats During The Development Of Hypertension

Background: Although renal mitochondrial dysfunction has been observed in various models of hypertension, the events leading to this dysfunction remain unclear. The present study focused on the role of salt (NaCl) intake upon renal mitochondrial bioenergetic function in Dahl salt-sensitive (SS) rats hypothesizing that a high salt (HS) diet would impair mitochondrial bioenergetics via stimulation of NOX-induced oxidative stress. Method: The HS induced progressive alteration of oxidative phosphorylation (OxPhos) and ATP synthesis in mitochondria obtained from renal cortex and outer medulla (OM) of male SS rats were compared to those of SS rats with dual knockout of NOX4 and p67 phox subunit of NOX2 (NOX DKO). Mitochondria were isolated from the cortex and OM of groups of age matched rats fed a 0.4% NaCl (LS) diet since weaning and at days 3, 7, 14 & 21 of a 4.0% NaCl (HS) diet feeding. ADP-induced (state 3) O 2 consumption rates (OCR) were measured in mitochondria energized with pyruvate and malate as substrates using an Oroboros Oxygraph-2k Instrument. Results: In SS rats, a biphasic pattern in state 3 OCR was observed with progressive uncoupling of OxPhos occurring in both cortex and OM. In the early phase of hypertension (days 3 & 7), state 3 OCR was increased (155 ± 8.2 to 190 ± 12.2 to 203.4 ± 12.1 nmol/min/mg in cortex and 101.4 ± 5.1 to 121.8 ± 7.3 to 112.8 ± 6.8 nmol/min/mg in OM; n = 5). In the established phase of hypertension (days 14 & 21), this increase was not sustained as state 3 OCR was reduced to 153 ± 7.65 and 132 ± 6.6 nmol/min/mg in cortex and 105 ± 7.3 and 63.3 ± 6.5 nmol/min/mg in OM. In contrast, SS NOX DKO rats fed a HS diet showed no significant differences in state 3 OCR in both cortex and OM, as was also observed in a control group of age matched NOX DKO rats maintained on a LS diet throughout the study. Conclusions: In SS rats, a HS diet causes initial increase in the efficiency of OxPhos for ATP production followed by a progressive decrease in the efficiency of OxPhos for ATP production in the established phase of hypertension. This biphasic pattern with ultimate reduction in the efficiency of OxPhos for energy production was not observed in SS NOX DKO rats demonstrating the important causal role of NOX-induced oxidative stress in the renal mitochondrial bioenergetic dysfunction.