Characterization Of Na Research Articles

Characterization of Na and K Level in Ujjaini River Water in Amethi, UP, India

Abstract: Ujjaini River is the main source of water for aquatic life and household things related to human beings. The traditional living drinking water quality assessment can evaluate wholly the impact of river water quality on human body. Drinking water safety is an important part in water scientific field. In the presented study a number of water samples were collected from selected sites of Ujjaini River in Amethi, UP India in the month of August-2020. The collected water samples were carried out to the laboratory to analyze the Na and K level to check the suitability of water for drinking and cooking purposes, by using standard procedures. People usually identify River water pollution when people start getting sick while drinking it, once discovered River water pollution needs to be addressed, both to clean the contaminated water and to prevent its spread. At result it was found that these parameters were present in permissible limits according to the BIS and WHO standards yet we should check the quality of River water time to time. People can help to prevent the River water pollution by disposing of hazardous materials like oil, paints, unused prescriptions and solvents responsible in a facility which is certified to handle such materials.

Characterization of Na+ currents regulating intrinsic excitability of optic tectal neurons.

Developing neurons adapt their intrinsic excitability to maintain stable output despite changing synaptic input. The mechanisms behind this process remain unclear. In this study, we examined Xenopus optic tectal neurons and found that the expressions of Nav1.1 and Nav1.6 voltage-gated Na+ channels are regulated during changes in intrinsic excitability, both during development and becsuse of changes in visual experience. Using whole-cell electrophysiology, we demonstrate the existence of distinct, fast, persistent, and resurgent Na+ currents in the tectum, and show that these Na+ currents are co-regulated with changes in Nav channel expression. Using antisense RNA to suppress the expression of specific Nav subunits, we found that up-regulation of Nav1.6 expression, but not Nav1.1, was necessary for experience-dependent increases in Na+ currents and intrinsic excitability. Furthermore, this regulation was also necessary for normal development of sensory guided behaviors. These data suggest that the regulation of Na+ currents through the modulation of Nav1.6 expression, and to a lesser extent Nav1.1, plays a crucial role in controlling the intrinsic excitability of tectal neurons and guiding normal development of the tectal circuitry.

Synthesis, crystal structure, and characterization of Na2SrV4O12: A low‐firing dielectric vanadate

AbstractIn this work, cyclotetravanadate Na2SrV4O12 was synthesized at a relatively low sintering temperature of ∼500°C using a solid‐state reaction method. X‐ray diffraction and a transmission electron microscope characterization featured a tetragonal structure that was built by a 3D frame of isolated tetracyclic (V4O12)4−. Dielectric measurements demonstrated strong dependence on frequency and temperature. A low relative permittivity of εr ∼ 8 ± 0.2 and a dielectric (loss tanδ) ∼ 0.4 ± 0.01 was achieved at a frequency of 10 kHz and room temperature. ac impedance and conductivity analysis revealed a thermally activated migration behavior of charge carriers with a short‐range hopping feature. XPS analysis validated the existence of oxygen vacancy and reduction in vanadium (from V5+ to V4+), which gave rise to charged lattice defects. The migration or hopping of such charged defects was responsible for the observed electrical behaviors. Owing to the simple composition, inexpensive raw materials and low density (2.99 g/cm3) make Na2SrV4O12 ceramic a potential candidate for lightweight devices and in photocatalytic degradation and all‐solid‐state ion batteries.

Purification of Crude Bentonite Clay: Synthesis and Characterization of Na, Mg and Cu Incorporated Bentonite Clay

Commercially available natural bentonite clay samples obtained from Oil India Limited, India, were purified via standard sedimentation process followed by screening with the help of siphoning process by applying Stock’s law to obtain < 2 μm fraction of the clay. The Na+, Mg2+ and Cu2+ cations were incorporated in the interlayers of the bentonite clay by applying different chemical procedures. Modified bentonite clays thus obtained were characterized by PXRD, HRTEM, FTIR analysis, DRS analysis, TGA, SEM & EDX analysis, and BET surface area analysis.

The Structural, Lattice Dynamic, Thermodynamic and Mechanical Characterization of Na <sub>2</sub>Mo <sub>2</sub>O <sub>7</sub> Crystal by First-Principles Calculation

The Structural, Lattice Dynamic, Thermodynamic and Mechanical Characterization of Na <sub>2</sub>Mo <sub>2</sub>O <sub>7</sub> Crystal by First-Principles Calculation

Hydrochemical Characteristics Jointly Determine the Transport and Cycling of Soil Carbon, Nitrogen, and Phosphorus in an Arid Chinese Wetland

AbstractSalt accumulation gradually changes the cycling of carbon (C), nitrogen (N), and phosphorus (P) and may even transform sinks into sources in arid wetlands. However, it's not clear how hydrochemical characteristics affect the wetland's source or sink function or how they affect C, N, and P cycling in arid regions. To clarify these relationships, we conducted field measurement in arid northern China. We simulated the variations of hydrochemical characteristics and the storage and stoichiometry of C, N, and P using the process‐based DeNitrification‐DeComposition (DNDC) and Hydrus‐1D models. The meteorological and hydrological processes had obvious characteristics of seasonal and interannual changes. The measured evapotranspiration averaged 660.23 and 587.94 mm year−1 in the saltmarsh and riparian wetlands, respectively. The soil showed a clear trend with higher SO42−, Na+, Ca2+, and Cl− fractions in comparison with lower Mg2+, K+, and HCO3− fractions, with the major ion and nutrient concentrations gradually decreasing with increasing depth in the soil. The major ion types had characteristics of Na+‐Ca2+‐SO42−‐Cl− in the saltmarsh wetland and riparian wetland. The storage of total C, N, and P were 372.72 ± 66.52 t C/hm2, 10.92 ± 2.59 t N/hm2, and 17.55 ± 1.54 t P/hm2 in the saltmarsh wetland versus 119.72 ± 27.88 t C/hm2, 4.38 ± 1.24 t N/hm2, and 13.17 ± 1.46 t P/hm2 in the riparian wetland. Therefore, wetland salinization in our study led to increased soil C, N, and P contents and storage and thereby enhanced the sink function of the wetlands.

Synthesis and characterization of Na+ conducting glass-ceramic Na5FeSi4O12 doped with boron, aluminum, and gallium oxides

Sodium-ion conductive glass-ceramics of Na5FeSi4O12 were successfully synthesized through the crystallization of glasses with the composition Na5FeSi4O12. The optimum crystallization conditions and the kinetics of the glasses were examined by differential thermal analysis. The characterization of crystallization and conduction properties were performed on thus obtained glass-ceramic Na5FeSi4O12 by a non-isothermal modified Kissinger and complex impedance methods, respectively. The activation energy for crystallization was 279 kJ mol−1 and the sodium-ion conductivity was obtained as 1.33 × 10−3 S cm−1 at 300 °C. To improve the conductivity with a small amount of Si-substitutes, Na5FeSi4O12-isostructural derivatives containing such as B, Al, and Ga were also prepared according to the same crystallization process of glasses with the composition Na5.1FeM0.1Si3.9O12 (M = B, Al, Ga). Without phase separation, the ionic conductivities of glass-ceramics were enhanced up to 1.69 × 10−3 at 300 °C on Na5.1FeB0.1Si3.9O12, whereas decreased down to 1.30 × 10−3 and 1.12 × 10−3 S cm−1 at 300 °C on Na5.1FeAl0.1Si3.9O12, and Na5.1FeGa0.1Si3.9O12, respectively.

Amendments to saline-sodic soils showed long-term effects on improving growth and yield of rice (Oryza sativa L.).

BackgroundSaline-sodic soils are widely distributed in arid and semi-arid regions around the world. High levels of salt and sodium inhibit the growth and development of crops. However, there has been limited reports on both osmotic potential in soil solutions (OPss) and characteristics of Na+ and K+ absorption in rice in saline-sodic soils under various amendments application.MethodsA field experiment was conducted between 2009 and 2017 to analyze the influence of amendments addition to saline-sodic soils on rice growth and yield. Rice was grown in the soil with no amendment (CK), with desulfurization gypsum (DG), with sandy soil (SS), with farmyard manure (FM) and with the mixture of above amendments (M). The osmotic potential in soil solution, selective absorption of K+ over Na+ (SA), selective transport of K+ over Na+ (ST), the distribution of K+ and Na+and yield components in rice plants were investigated.ResultsThe results indicated that amendments application have positive effects on rice yield. The M treatment was the best among the tested amendments with the highest rice grain yield. M treatment increased the OPss values significantly to relieve the inhibition of the water uptake by plants. Additionally, the M treatment significantly enhanced K+ concentration and impeded Na+ accumulation in shoots. SA values were reduced while ST values were increased for all amendments. In conclusion, a mixture of desulfurization gypsum, sandy soil and farmyard manure was the best treatment for the improvement of rice growth and yield in the Songnen Plain, northeast China.

Adaptation of Plants to Salt Stress: Characterization of Na+ and K+ Transporters and Role of CBL Gene Family in Regulating Salt Stress Response

Salinity is one of the most serious factors limiting the productivity of agricultural crops, with adverse effects on germination, plant vigor, and crop yield. This salinity may be natural or induced by agricultural activities such as irrigation or the use of certain types of fertilizer. The most detrimental effect of salinity stress is the accumulation of Na+ and Cl− ions in tissues of plants exposed to soils with high NaCl concentrations. The entry of both Na+ and Cl− into the cells causes severe ion imbalance, and excess uptake might cause significant physiological disorder(s). High Na+ concentration inhibits the uptake of K+, which is an element for plant growth and development that results in lower productivity and may even lead to death. The genetic analyses revealed K+ and Na+ transport systems such as SOS1, which belong to the CBL gene family and play a key role in the transport of Na+ from the roots to the aerial parts in the Arabidopsis plant. In this review, we mainly discuss the roles of alkaline cations K+ and Na+, Ion homeostasis-transport determinants, and their regulation. Moreover, we tried to give a synthetic overview of soil salinity, its effects on plants, and tolerance mechanisms to withstand stress.

Hydrogeochemical studies and suitability assessment of groundwater quality for irrigation at Warri and environs., Niger delta basin, Nigeria

The quality of groundwater for irrigation was assessed in Warri and the surrounding area using America Public Health Association standard (APHA) method of analysis. The following results were obtained from different constituents that influence the water quality for irrigation. Electrical Conductivity was found within the range 207–1163, Soluble Sodium Percentage (SSP) was found between 1.12 and 218.75, Sodium Percentage (Na%) from 2.56 to 280.00, Permeability Index (PI) was found within 0.00–5.75, Sodium Adsorption Ratio (SAR) ranges from 0.02 to 1.31, Residual Sodium Bicarbonate (RSBC) ranges from −0.17 to 0.26, Kelly's Ratio (KR) ranges from 0.02 to 133.33, Total Hardness (TH) ranges from 5.5 to 84. Comparing the above estimated result with the various permissible standard values for irrigation, SSP, Na% and Ec were found to be slightly above the standard values at some locations while all other constituents were found to satisfy the standard value for irrigation. The groundwater facies analysis plotted with Chadha revealed that the water shows little characteristics of Na+ + HCO3- and Na+ + Cl− water types, while for Gibbs plot, it revealed that groundwater chemistry is controlled dominantly by rock weathering processes.

Characterization of Na+ exclusion mechanism in rice under saline-alkaline stress conditions

This study was designed to elucidate the physiological responses of two rice genotypes to different pH levels under high saline stress. A salt-tolerant cultivar, FL478, and a salt-sensitive cultivar, IR29, were exposed to saline-alkaline solutions supplemented with 50 mM Na at pH 9 (severe), pH 8 (moderate), and pH 7 (mild) for three weeks. The results indicated that FL478 is relatively saline-alkaline tolerant compared to IR29, and this was evident from its higher dry mass production, lower Na+ concentration in the leaf blades, and maintenance of water balance under both mild and moderate saline-alkaline stress conditions. In both cultivars, Na+ concentrations in the leaf blades were considerably higher at pH 8 than at pH 7, indicating that high alkaline stress promoted Na+ accumulation under highly saline conditions. FL478 plants had lower Na+/K+ ratios in leaf blades and leaf sheaths than IR29 plants under saline-alkaline stress at both pH 7 and pH 8. To understand the mechanisms behind the difference in saline-alkaline tolerance between the two rice genotypes, transcript levels of the genes encoding Na+ transport proteins were analyzed. In response to mild and moderate saline-alkaline stress conditions, salt-tolerant FL478 had highly induced expression of the OsHKT1;5 gene in the roots, corresponding to lower Na+ accumulation in the leaf blades. Induction of high expression of the OsSOS1 gene in the roots of FL478 implied that Na may be effectively exported from cytosols to apoplasts in the roots resulting in sequestration of Na+ to outside of the roots and loading Na+ in xylem transpiration stream. On the other hand, the salt-sensitive IR29 had lower expression of the genes related to Na+ transporters, such as the OsHKT1;5 gene and the OsSOS1 gene, in the roots, leading to higher Na+ accumulation in the shoots. Expression of the determinant genes for alkaline tolerance, such as K+ and Fe acquisition and acidification of the rhizosphere was highly induced in FL478, but not in IR29. Thus, molecular analysis suggested that genes encoding Na+ transport proteins are involved in regulating Na+ transport under saline-alkaline stress in both salt-tolerant and salt-sensitive rice cultivars, and this is useful information for improving saline-alkaline tolerance traits of rice in the future.

Abrupt Change in Electrophysiological Properties Begins From Postnatal Day 7 Before Hearing Onset in the Developing Mice Auditory Cortical Layer II/III Neurons.

ObjectivesIn the developing auditory cortex, maturation of electrophysiological properties and cell types before and after hearing onset has been reported previously. However, the exact timing of firing pattern change has not been reported. In this study, firing pattern change was investigated from postnatal day 3 (P3) to P12 in auditory cortical layer II/III neurons to investigate whether firing pattern changes dramatically after a specific point during development.MethodsICR mice pups aged from P3 to P12 were sacrificed to obtain 300-mm-thick brain slices containing the primary auditory cortex. From cortical layer II/III neurons, the patterns of action potential firing generated by current injection were examined using whole cell current clamp technique and the characteristics of Na+ currents involved in action potential firing were investigated using whole cell voltage clamp technique.ResultsFrom P3 to P6, most cells did not show action potential firing (29 of 46 cells), and some cells responding to current injection showed a single action potential at the initial depolarizing current step (17 of 46 cells). This firing pattern changes from P7. From P7 to P9, cells begin to show regular spiking to current injection. The spiking frequency increased after P10. In studying Na+ current with whole cell voltage clamp, Na+ current densities increased gradually (32.0±2.0 pA/pF [P3–P6, n=7], 51.2±2.0 pA/pF [P7–P9, n=13], and 69.5±3.7 pA/pF [P10–P12, n=13]) in low external [Na+] condition. Na+ current recovery was accelerated and inactivation curves shifted to hyperpolarization with age.ConclusionAs regular spiking cells were observed from P7 but never from P3 to P6, P7 might be regarded as an important milestone in the development of auditory cortical layer II/III neurons. This change might mainly result from the increase in Na+ current density.

Abstract 341: Prolonged Post-Differentiation Culture Influences the Biophysics of Na + - And Ca 2+ Channels in Induced Pluripotent Stem Cell-Derived Cardiomyocytes

Background: Cardiomyocytes (CM), derived from human induced-pluripotent stem cells (iPSC-CM), are promising tools for in vitro proarrhythmia screening for drug safety. However, among various challenges with interpretation of iPSC-CM experimental results, the influence of varied culture periods post-differentiation on the electrophysiological properties of iPSC-CMs is unclear. Objective: To test the hypothesis that prolonged post-differentiation culture of iPSC-CMs will influence the biophysical characteristics of Na + - and Ca 2+ -channels. Methods: Using whole-cell patch clamp, we compared the electrophysiological properties of differentiated ventricular-like iPSC-CMs (APD 30-40 /APD 70-80 >1.5) cultured for 10 to 15 days (D10-15) to those cultured for more than 30 days (≥ D30) both under current- and voltage- clamp configurations. Quantitative real-time PCR was used to quantify the mRNA expression of voltage-gated Na channel subunits SCN1A, SCN5A and Ca channel subunits CACNA1C, CACNA1G and CACNA1I. Fold change was calculated by 2 -ΔΔCt method. Data were analyzed by Student’s t test, and P value <0.05 was considered significant. Results: Post-differentiation prolonged culture imparts increased cellular excitability with high frequency spontaneous action potentials, robust increase in the magnitude of peak Na + -current level, relatively shallow inactivation kinetics of Na + channels, faster recovery from inactivation, and augmented Ca 2+ current density compared to early cultured iPSC-CM. This was associated with a greatly enhanced mRNA expression of α-subunit transcripts of SCN1A (7.5 fold) and SCN5A (38 fold) Na channel subtypes while less robust elevation in the mRNA expression of CACNA1C (0.5 fold), CACNA1G (2 fold) and CACNA1I (2 fold) subunits in prolonged culture compared to early cultured iPSC-CM. Conclusion: Prolonged culture of ventricular-like iPSC-CMs affects the excitability, single-cell electrophysiological properties and differential ion channels subunit expression. Standardization of post-differentiation period for ventricular-like iPSC-CMs culture is crucial for in vitro proarrhythmia screening, health/disease modelling to study cellular mechanisms or test high-throughput drugs’ efficacy and toxicity.

Hydrothermal process of synthetic gibbsite and the characteristics of Na in gibbsite crystal

The presence of Na in synthetic gibbsite was studied by several modern testing methods such as X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy and inductively coupled plasma. Results show that Na is located between gibbsite crystals and is not present as sodium aluminosilicate hydrate in synthetic gibbsite. Synthetic gibbsite crystal can be transformed into boehmite under the hydrothermal condition of 210 °C for 60 min. During the reaction process, synthetic gibbsite crystal particles break up into small fragments and form boehmite. During the process, impurities are released and the Na can be removed by washing. Over 90% of Na can be removed during the hydrothermal transformation process. This technology can be applied in the production process of high-purity alumina.

Preparation and characterization of Na and F co-doped hydroxyapatite coating reinforced by carbon nanotubes and SiC nanoparticles

Carbon nanotubes and SiC nanoparticles reinforced Na and F co-doped hydroxyapatite coating (CS-NFH) was fabricated by electrochemical deposition method. The morphology, microstructure, shear strength, wettability and in-vitro bioactivity of CS-NFH coating were analyzed. Homogeneous and crackfree CS-NFH coatings composed of spherical particles were achieved. The shear strength for CS-NFH was 9.04 MPa, which was more than twice the value of that for pure hydroxyapatite coating. Wettability test showed CS-NFH coating had super-hydrophilicity surface with water contact angle of 0°. The in-vitro bioactivity test showed that the coating could induce the formation of new apatite in simulated body fluid. CS-NFH may have potential application as coating materials in orthopaedic applications.

Characterization of Na+ transport to gain insight into the mechanism of acid-base and ion regulation in white sturgeon (Acipenser transmontanus)

Freshwater fish actively take up ions via specific transporters to counter diffusive losses to their hypotonic environment. While much is known about the specific mechanisms employed by teleosts, almost nothing is known about the basal fishes, such as white sturgeon (Acipenser transmontanus) which may offer insight into the evolution of osmo- and ionoregulation in fishes. We investigated Na+ uptake in juvenile white sturgeon in the presence and absence of transporter inhibitors. We found that sturgeon acclimated to 100μmoll−1 Na+ have Na+ uptake kinetics typical of teleosts and that a Na+/H+ exchanger (NHE) is the predominant transporter for Na+ uptake. White sturgeon are tolerant to hypercarbia-induced respiratory acidoses and recover blood pH (pHe) at 1.5kPa PCO2 but not at higher PCO2 (6kPa PCO2) where they preferentially regulate intracellular pH (pHi). It was hypothesized that during exposure to hypercarbia Na+ uptake would increase at CO2 tensions at which fish were capable of pHe regulation but decrease at higher tensions when they were preferentially regulating pHi. We found that Na+ uptake did not increase at 1.5kPa PCO2, but at 6kPa PCO2 Na+ uptake was reduced by 95% while low water pH equivalent to 6kPa PCO2 reduced Na+ uptake by 71%. Lastly, we measured net acid flux during hypercarbia, which indicates that net acid flux is not associated with Na+ uptake. These findings indicate Na+ uptake in sturgeon is not different from freshwater teleosts but is sensitive to hypercarbia and is not associated with pHe compensation during hypercarbia.

Synthesis and characterization of Na(Gd0.5Lu0.5)F4: Nd3+,a core-shell free multifunctional contrast agent

Compared to conventional core-shell structures, core-shell free nanoparticles with multiple functionalities offer several advantages such as minimal synthetic complexity and low production cost. In this paper, we present the synthesis and characterization of Nd3+ doped Na(Gd0.5Lu0.5)F4 as a core-shell free nanoparticle system with three functionalities. Nanocrystals with 20 nm diameter, high crystallinity and a narrow particle size distributions were synthesized by the solvothermal method and characterized by various analytical techniques to understand their phase and morphology. Fluorescence characteristics under near infrared (NIR) excitation at 808 nm as well as X-ray excitation were studied to explore their potential in NIR optical and X-ray imaging. At 1.0 mol% Nd concentration, we observed a quantum yield of 25% at 1064 nm emission with 13 W/cm2 excitation power density which is sufficiently enough for imaging applications. Under 130 kVp (5 mA) power of X-ray excitation, Nd3+ doped Na(Gd0.5Lu0.5)F4 shows the characteristic emission bands of Gd3+ and Nd3+ with the strongest emission peak at 1064 nm due to Nd3+. Furthermore, magnetization measurements show that the nanocrystals are paramagnetic in nature with a calculated magnetic moment per particle of ∼570 μB at 2T. These preliminary results support the suitability of the present nanophosphor as a multimodal contrast agent with three imaging features viz. optical, magnetic and X-ray.

ChemInform Abstract: Single Crystal Growth and Characterization of NaxLn1‐xMoO4, Ln: La, Ce, Pr, Nd, Sm, and Eu (x: 0.397—0.499).

AbstractSingle crystals of the reduced lanthanoid‐containing compounds La0.516Na0.484MoO4, Ce0.512Na0.488MoO4, Pr0.502Na0.498MoO4, Nd0.501Na0.499MoO4, Sm0.509Na0.491MoO4, and Eu0.603Na0.397MoO4 are grown from a NaCl/CsCl eutectic flux by in‐situ reduction using 2:1:0.5 molar mixtures of MoO3, Ln2O3, and Mo, the latter acting as reducing agent (evacuated silica tubes, 825 °C, 24 h; cooling to 450 °C at a rate of 6 °C/h).

Characterization of Na+-K+-2Cl- Cotransporter Activity in Rabbit Lacrimal Gland Duct Cells.

PurposeWe recently reported that isolated duct segments from rabbit lacrimal gland (LG) were able to secrete fluid in response to secretagogues, which were blocked completely by bumetanide. This suggests the functional involvement of Na+-K+-2Cl− cotransporter (NKCC1) in ductal fluid secretion. Therefore, the aim of this study was to investigate the activity profile of NKCC1 in isolated rabbit LG duct segments.MethodsInterlobular ducts were isolated from fresh rabbit LG tissue. Microfluorometry with the ammonium (NH4+)–pulse technique was used to elicit pH changes in duct cells, and the rate of bumetanide-sensitive cytosolic acidification after addition of NH4+ was used to quantify the activity of NKCC1.ResultsWhile basal activity of NKCC1 was undetectable, low cytosolic chloride (Cl−) level and hyperosmotic challenge (390 mOsm) were able to increase the activity of NKCC1. Carbachol (100 μM) had no significant effect on NKCC1 activity. Elevation of cytosolic calcium (Ca2+) level with Ca2+-ionophore (A 23187, 1 μM) did not cause any alteration in the activity of the cotransporter while direct activation of protein kinase C (phorbol myristate acetate, 100 nM) increased its activity slightly but in a significant manner. Addition of either forskolin (10 μM), cell-permeable cAMP analogue (8-bromo cAMP, 100 μM) or vasoactive intestinal peptide (200 nM) resulted in a significant increase in the activity of NKCC1.ConclusionsThese results highlight the functional involvement of NKCC1 in LG duct secretion. These findings may facilitate our understanding of LG function and may contribute to the development of targeted pharmacologic interventions in case of dry eye disease.

Cloning and characterization of Na(+)/H(+) Exchanger isoforms NHE2 and NHE3 from the gill of Pacific dogfish Squalus suckleyi.

Na(+)/H(+) Exchanger (NHE) proteins mediate cellular and systemic homeostasis of sodium and acid and may be the major sodium uptake method for fishes. We cloned and sequenced NHE2 and NHE3 from the gill of the North Pacific Spiny Dogfish shark Squalus suckleyi and expressed them in functional form in NHE-deficient (AP-1) cell lines. Estimated IC50 for inhibition of NHE activity by amiloride and EIPA were 55 μmol l(-1) and 4.8 μmol l(-1), respectively, for NHE2 and 9 μmol l(-1) and 24 μmol l(-1), respectively, for NHE3. Phenamil at 100 μmol l(-1) caused less than 16% inhibition of activity for each isoform. Although the IC50 are similar for the two isoforms, dfNHE2 is less sensitive than human NHE2 to inhibition by amiloride and EIPA, while dfNHE3 is more sensitive than human NHE3. These IC50 estimates should be considered when selecting inhibitor doses for fishes and for reinterpretation of previous studies that use these pharmacological agents.