The effect of enternal sodium concentration upon sodium fluxes in Chironomus dorsalis (Meig.) and Camptochironomus tentans (Fabr.), and the effect of other ions on sodium influx in C. tentans.

In comparison with other freshwater animals, the sodium uptake mechanism in fourth instar larvae of both C. tentans and C. dorsalis has a moderate affinity for sodium. In both species half maximum influx (Km) occurs at about 0.57 mM-Na+ and is unaltered by salt depletion. Maximum influx is achieved in steady-state C. tentans at 1.9 mM-Na+, and in steady-state C. dorsalis at 3.0 mM-Na+. Both of these values increase on depletion. Efflux also appears to be saturable at higher external sodium concentrations. In C. tentans, sodium may be transported independently of chloride, although it seems likely that sodium movement is enhanced by chloride. Sulphate strongly inhibits sodium influx. Nitrate apparently inhibits sodium influx at low concentrations, but this inhibition is progressively overcome at external sodium concentrations approaching 4 mM. A number of cations interfere with sodium influx in depleted C. tentans, notably H+, Li+ and, to a lesser extent NH4+. It is suggested that these ions compete with sodium for carrier sites. Potassium is apparently transported independently of sodium.     

The relationship between transepithelial sodium movement and potential difference in the larva of Camptochironomus tentans (Fabr.) and some observations on the accumulation of other ions.

In fourth instar larvae of Camptochironomus tentans, net sodium uptake from 2 mM-NaCl has an electrogenic component. During net uptake the transepithelial potential (TEP) alters from a value of approximately - 40 mV (sign refers to haemolymph), in depleted animals, to approximately o mV. The TEP in depleted larvae is dependent upon external sodium concentration above about I mM-Na+, becoming increasingly electropositive (haemolymph relative to medium) at high sodium concentrations. This effect is exaggerated in Na2SO4 compared with NaCl. At an external concentration of 2mM-NaCl, chloride is carried by an electroneutral mechanism, probably a closely coupled Cl-/anion exchange. However, it is possible that chloride transport could become somewhat electrogenic at higher concentrations. Lithium competes with sodium for the electrogenic pump. Observed TEPs differ greatly from those required to maintain passively the haemolymph concentrations of sodium and chloride.     

Schistosoma mansoni: preparation, characterization of (Na+ + K+)ATPase from tegument and carcass

The preparation and some biochemical properties of a (Na+ + K+)ATPase from male adult Schistosoma mansoni are described. After incubation in a membrane disruption medium, the tegument and carcass of the worms were separated and treated to obtain fractions enriched in (Na+ + K+)ATPase. The activity of the tegumental ouabain sensitive (Na+ + K+)ATPase at 37 C was 20.3 mumole Pi X mg-1 protein X hr-1 and represented 32% of the total ATPase activity. The (Na+ + K+)ATPase prepared from the carcass had a lower specific activity (3.7 mumole Pi X mg-1 protein X hr-1) but a higher relative activity (55%). Similar concentrations of Na+ and K+ activated the enzymes from both sources, and both enzymes were inhibited by similar concentrations of calcium. However, the enzyme from carcass was ten times more sensitive to ouabain than the enzyme from tegument. Comparison with results obtained on the (Na+ + K+)ATPase of human heart showed that the enzymes from the worms were more resistant to ouabain. The half maximal inhibitory concentration of dihydroouabain compared to that of ouabain was also different in the enzymes from human and worm. We conclude that (1) there exists at least one structural difference between the (Na+ + K+)ATPase of S. mansoni and that of the human host, and (2) it is useful to separately study the enzymes from tegument and carcass because they differ in sensitivity to cardiac glycosides.     

Characterization of gill (Na+ + K+)-ATPase in the sea bass (Dicentrarchus labrax L.)

Bass gill microsomal preparations contain both a Na+, K+ and Mg2+-dependent ATPase, which is completely inhibited by 10(-3)M ouabain and 10(-2)M Ca2+, and also a ouabain insensitive ATP-ase activity in the presence of both Mg2+ and Na+. Under the optimal conditions of pH 6.5, 100 mM Na+, 20 mM K+, 5 mM ATP and 5 mM Mg2+, (Na+ + K+)-ATPase activity at 30 degrees C is 15.6 mumole Pi hr/mg protein. Bass gill (Na+ + K+)-ATPase is similar to other (Na+ + K+)-ATPases with respect to the sensitivity to ionic strength, Ca2+ and ouabain and to both Na+/K+ and Mg2+/ATP optimal ratios, while pH optimum is lower than poikilotherm data. The enzyme requires Na+, whereas K+ can be replaced efficiently by NH+4 and poorly by Li+. Both Km and Vm values decrease in the series NH+4 greater than K+ greater than Li+. The break of Arrhenius plot at 17.7 degrees C is close to the adaptation temperature. Activation energies are scarcely different from each other and both lower than those generally reported. The Km for Na+ poorly decreases as the assay temperature lowers. The comparison with literature data aims at distinguishing between distinctive and common features of bass gill (Na+ + K+)-ATPase.     

Sodium relations in Chenopodiaceae: a comparative approach

Sodium relations of 15 species of Chenopodiaceae were studied in seedlings grown on quartz sand at 10 mol m^?3 of sodium and potassium. Uptake of sodium and potassium into whole plants and shoots was followed over 2 weeks. High alkali ion uptake rates were found in all species. The apparent selectivity of alkali ion uptake showed a continuous variation between species, from nearly perfect sodium exclusion to negligible cation selection. K/Na ratios above 6 were found in the shoots of eight species. For most of these plants above ground sodium concentrations were highest in the hypocotyls. However, in Chenopodium hybridum (shoot K/Na = 10) and C. urbicum (shoot K/Na = 17) above ground sodium concentrations were lowest in hypocotyls and highest in leaves, as in those species accumulating larger amounts of sodium. These differences are discussed with respect to the underlying mechanisms of ion regulation.     

Ionic fluxes in isolated epithelial cells of the abdominal skin of the frog Leptodactylus ocellatus.

Unidirectional ion fluxes are measured in cells isolated by a trypsination-dissection method from the epithelium of the frog Leptodactylus ocellatus. Potassium seems to be contained in a single cellular compartment. The influx of potassium is 0.0068 mumole min-1 mg-1 of dry weight and is carried by a ouabain-sensitive pump. Sodium seems to be contained in two cellular compartments, one of which does not exchange its Na within the experimental period. The possibility that these compartments reflect the existence of different types of cells is not discarded. 49% of the rate constant for the Na efflux is ouabain-sensitive and 23% is ethacrynic-sensitive. Under control conditions the permeability to potassium (PK), sodium (PNa) and chloride (PC1) are 7.6 X 10(-5), 2.6 X 10(-5) and 2.8 X 10(-5) liters/min mg, respectively. The value of PNa is much higher than predicted by current electrical models of the epithelium. The discrepancy might offer some insight into the nature of the "inner facing barrier" of the skin.     

Sodium and potassium fluxes and membrane potential of human neutrophils: evidence for an electrogenic sodium pump

Sodium and potassium ion contents and fluxes of isolated resting human peripheral polymorphonuclear leukocytes were measured. In cells kept at 37 degrees C, [Na]i was 25 mM and [K]i was 120 mM; both ions were completely exchangeable with extracellular isotopes. One-way Na and K fluxes, measured with 22Na and 42K, were all approximately 0.9 meq/liter cell water . min. Ouabain had no effect on Na influx or K efflux, but inhibited 95 +/- 7% of Na efflux and 63% of K influx. Cells kept at 0 degree C gained sodium in exchange for potassium ([Na]i nearly tripled in 3 h); upon rewarming, ouabain-sensitive K influx into such cells was strongly enhanced. External K stimulated Na efflux (Km approximately 1.5 mM in 140-mM Na medium). The PNa/PK permeability ratio, estimated from ouabain insensitive fluxes, was 0.10. Valinomycin (1 microM) approximately doubled PK. Membrane potential (Vm) was estimated using the potentiometric indicator diS-C3(5); calibration was based on the assumption of constant-field behavior. External K, but not Cl, affected Vm. Ouabain caused a depolarization whose magnitude dependent on [Na]i. Sodium-depleted cells became hyperpolarized when exposed to the neutral exchange carrier monensin; this hyperpolarization was abolished by ouabain. We conclude that the sodium pump of human peripheral neutrophils is electrogenic, and that the size of the pump-induced hyperpolarization is consistent with the membrane conductance (3.7-4.0 microseconds/cm2) computed from the individual K and Na conductances.     

Volume and ion regulating renal functions in the big gerbil (Rhombomys opimus L.) and the water vole (Arvicola terrestris L.)

1. After iso-osmotic salt loading (1% NaCl, 1.25% KCl, 0.75% MgCl2 solutions, each load making up 5% body weight) the water voles excreted 66.2% sodium, 84.4% potassium, 18.8% magnesium over a 4 hr period. The big gerbil excreted 20%, 58.9% and 7.1% respectively over the same period. The volume of the water excreted was greater in the case of the water vole. 2. There were no considerable changes in plasma ion concentration in rodents of the species studied after salt loading. 3. The gerbils and water voles had no significant changes in the renal cortex electrolyte concentrations as a result of isotonic salt loads. The highest sodium cortico-papillar gradient was found in the gerbils when experimenting with the isotonic NaCl loading. It was somewhat lower with the KCl load, and significantly lower with water and MgCl2 loads. 4. Under the same experimental conditions, no major changes in the papilla sodium concentration were found in the water voles. 5. The concentrations of potassium, calcium and magnesium were practically alike in all zones of the renal tissue of both rodent species, ion loads producing no effect. 6. The comparison of the renal volume and ion regulating function in rodents with different urine osmotic concentration systems proves the independent existence of renal functions. The greater rate of renal fluid and ion excretion in the water voles is coupled with less specific ion regulation.     

Salt Secretion in Aeluropus litoralis (Willd.) Parl.

The effect of ion composition and concentration in the rootmedium on salt secretion by Aeluropus litoralis was investigated.The presence of a high ionic concentration in the medium stimulatedthe secretion process. The sodium concentration in the secretedfluid was found to be always higher than its concentration inthe medium. A positive correlation was found between the outersodium chloride concentration and the amount of sodium secretedand/or leaf contents. Sodium secretion exhibited a high efficiencyin excluding excess sodium from leaftissues. Sodium retentionin the leaves occurred in relatively low rates. The secretion mechanisms were found to be highly selective tosodium, opposing potassium and calcium. In contrast, potassiumand calcium were retained in the leaves to a greater degreethan sodium. Antagonistic relationships between sodium and potassiumand sodium and calcium were observed in secretion. The secreted fluid contains also various organic substances.Several interpretations to the results in connection with theproposed hypotheses to the mechanism of salt secretion werediscussed.     

Non-reciprocal interactions between K+ and Na+ ions in barley (Hordeum vulgare L.)

The interaction of sodium and potassium ions in the context of the primary entry of Na(+) into plant cells, and the subsequent development of sodium toxicity, has been the subject of much recent attention. In the present study, the technique of compartmental analysis with the radiotracers (42)K(+) and (24)Na(+) was applied in intact seedlings of barley (Hordeum vulgare L.) to test the hypothesis that elevated levels of K(+) in the growth medium will reduce both rapid, futile Na(+) cycling at the plasma membrane, and Na(+) build-up in the cytosol of root cells, under saline conditions (100 mM NaCl). We reject this hypothesis, showing that, over a wide (400-fold) range of K(+) supply, K(+) neither reduces the primary fluxes of Na(+) at the root plasma membrane nor suppresses Na(+) accumulation in the cytosol. By contrast, 100 mM NaCl suppressed the cytosolic K(+) pool by 47-73%, and also substantially decreased low-affinity K(+) transport across the plasma membrane. We confirm that the cytosolic [K(+)]:[Na(+)] ratio is a poor predictor of growth performance under saline conditions, while a good correlation is seen between growth and the tissue ratios of the two ions. The data provide insight into the mechanisms that mediate the toxic influx of sodium across the root plasma membrane under salinity stress, demonstrating that, in the glycophyte barley, K(+) and Na(+) are unlikely to share a common low-affinity pathway for entry into the plant cell.     

pH-dependent glycine uptake in the presence and absence of sodium ions from rat small intestine

Intestinal uptake of glycine in rats was stimulated 15-20% in the presence of 120 mM Na at pH 6.0 and below but around neutral pH, the amino acid uptake was augmented to 60% compared to that in the Na-free medium. Glycine uptake was 30% more at pH 5.5 compared to that at pH 7.3 in the absence of Na. Kinetic analysis revealed a decrease in Kt for glycine uptake (9.62 mM) at pH 5.5 compared to that at pH 7.3 (Kt = 16.67 mM) with no change in maximal velocity (1.51 mumole/10 min/g tissue) in Na-free buffer. Addition of -SH group reacting reagents to the incubation medium produced 36-58% inhibition of glycine uptake in the presence of Na. However, in absence of Na, inhibition of the order of 21-35% and 8-23% was observed at pH 5.5 and 7.0, respectively. These findings suggest that glycine uptake in rat intestine is influenced by pH and -SH groups are implicated in the process(es).     

Human and dog erythrocytes: relationship between cellular ATP levels, ATP consumption and potassium concentrations.

The intracellular K+/Na+ ratio of various mammalian cell types are known to differ remarkably. Particularly noteworthy is the fact that erythrocytes of different mammalian species contain entirely different potassium and sodium concentrations. The human erythrocyte is an example of the supposedly "normal" high potassium cell, while the dog erythrocyte contains ten times more sodium than potassium ions (Table I). Furthermore, this difference is sustained despite the plasma sodium and potassium concentrations being almost identical in both species (high Na+ and low K+). In spite of these inorganic ion differences, both human and dog erythrocytes contain 33% dry material (mostly Hb) and 67% water. Conventional cell theory would couple cellular volume regulation with Na+ and K+ dependent ATPase activity which is believed to control intracellular Na+/K+ concentrations. Since the high Na+ and low K+ contents of dog erythrocytes are believed to be due to the lack of the postulated Na/K-ATPase enzyme, they must presumably have an alternative mechanism of volume regulation, otherwise current ideas of membrane ATPase activity coupled volume regulation need serious reconsideration. The object of our investigation was to explore the relationship between ATPase activity, ATP levels and the Na+/K+ concentrations in human and dog erythrocytes. Our results indicate that the intracellular ATP level in erythrocytes correspond with their K+, Na+ content. They are discussed in relation to conventional membrane transport theory and also to Ling's "association-induction hypothesis", the latter proving to be a more useful basis on which to interpret results.     

The effects of perfusion of the cutaneous vasculature on sodium uptake across isolated frog skin

Perfusion of cutaneous capillaries in isolated frog skin may remove an unstirred layer along the basolateral membrane of the epidermis that may affect the rate of cutaneous Na(+) uptake. To test this hypothesis, the cutaneous artery and vein of a bullfrog were cannulated to allow perfusion of isolated flank skin while the rate of Na(+) influx was determined. Rates of sodium influx with and without perfusion were determined in the same experiment. Na(+) uptake increased by 59+/-4.8% during the 1st 0.5 h of perfusion relative to the control, pre-perfusion period and then remained at 26+/-5.3% above control values. Concomitant with the increase in sodium uptake, the transepithelial potential difference fell by ca. 10% within the 1st 0.5 h of perfusion. The amount of labeled sodium leaving the skin in the venous effluent decreased exponentially in the 1st 0.5 h of perfusion, suggesting a wash out of an unstirred layer within the interstitial fluid. Sodium in the venous outflow accounted for ca. 25% of the sodium uptake during each perfusion period. Perfusion of the cutaneous vasculature thus has a significant effect on Na(+) transport and may potentially play a role in the acute regulation of cutaneous ion transport.     

Role of sodium ions and their uptake by cells of cultured blue-green algae, Spirulina platensis and Spirulina maxima

The growth of the blue-green algae Spirulina platensis and Spirulina maxima, cultured in complete mineral Zarouk medium containing Na+ or Na+-deficient medium, was studied over a period of 24 h. The optical densities of S. platensis and S. maxima cells, determined during the last hour of exposure to sodium deficiency, amounted to 55.6 and 32.6%, respectively, of the optical densities of the same cells grown in complete Zarouk medium. Moreover, the cultures grown in Na+-deficient medium exhibited increased ability to take up sodium (which was low in S. platensis and S. maxima cells cultured in complete mineral medium). It is concluded that the two species studied are characterized by periodic, on the order of minutes, changes in the cellular uptake and release of sodium.     

A pharmacological analysis of high-affinity sodium transport in barley (Hordeum vulgare L.): a 24Na+/42K+ study

Soil sodium, while toxic to most plants at high concentrations, can be beneficial at low concentrations, particularly when potassium is limiting. However, little is known about Na(+) uptake in this 'high-affinity' range. New information is provided here with an insight into the transport characteristics, mechanism, and ecological significance of this phenomenon. High-affinity Na(+) and K(+) fluxes were investigated using the short-lived radiotracers (24)Na and (42)K, under an extensive range of measuring conditions (variations in external sodium, and in nutritional and pharmacological agents). This work was supported by electrophysiological, compartmental, and growth analyses. Na(+) uptake was extremely sensitive to all treatments, displaying properties of high-affinity K(+) transporters, K(+) channels, animal Na(+) channels, and non-selective cation channels. K(+), NH(4)(+), and Ca(2+) suppressed Na(+) transport biphasically, yielding IC(50) values of 30, 10, and <5 μM, respectively. Reciprocal experiments showed that K(+) influx is neither inhibited nor stimulated by Na(+). Sodium efflux constituted 65% of influx, indicating a futile cycle. The thermodynamic feasibility of passive channel mediation is supported by compartmentation and electrophysiological data. Our study complements recent advances in the molecular biology of high-affinity Na(+) transport by uncovering new physiological foundations for this transport phenomenon, while questioning its ecological relevance.     

Futile Na+ cycling at the root plasma membrane in rice (Oryza sativa L.): kinetics, energetics, and relationship to salinity tolerance

Globally, over one-third of irrigated land is affected by salinity, including much of the land under lowland rice cultivation in the tropics, seriously compromising yields of this most important of crop species. However, there remains an insufficient understanding of the cellular basis of salt tolerance in rice. Here, three methods of 24Na+ tracer analysis were used to investigate primary Na+ transport at the root plasma membrane in a salt-tolerant rice cultivar (Pokkali) and a salt-sensitive cultivar (IR29). Futile cycling of Na+ at the plasma membrane of intact roots occurred at both low and elevated levels of steady-state Na+ supply ([Na+]ext=1 mM and 25 mM) in both cultivars. At 25 mM [Na+]ext, a toxic condition for IR29, unidirectional influx and efflux of Na+ in this cultivar, but not in Pokkali, became very high [>100 micromol g (root FW)(-1) h(-1)], demonstrating an inability to restrict sodium fluxes. Current models of sodium transport energetics across the plasma membrane in root cells predict that, if the sodium efflux were mediated by Na+/H+ antiport, this toxic scenario would impose a substantial respiratory cost in IR29. This cost is calculated here, and compared with root respiration, which, however, comprised only approximately 50% of what would be required to sustain efflux by the antiporter. This suggests that either the conventional 'leak-pump' model of Na+ transport or the energetic model of proton-linked Na+ transport may require some revision. In addition, the lack of suppression of Na+ influx by both K+ and Ca2+, and by the application of the channel inhibitors Cs+, TEA+, and Ba2+, questions the participation of potassium channels and non-selective cation channels in the observed Na+ fluxes.     

On the interaction of NH+4 and Na+ fluxes in the isolated trout gill.

1. Sodium influx was measured in isolated, previously perfused gill arches of rainbow trout, Salmo gairdneri, by measuring incorporation of 22Na into gill tissue following timed exposure to a 1 mM 22NaCl medium. Transport rates approximated those estimated for intact fish and were linear for at least one min. 2. NH4Cl-containing perfusates at pH 7 and 8 stimulated Na+ influx equally, indicating that only ionized ammonia is important in the transport process. A Na+/NH4+ exchange at basal and/or lateral membranes of the transporting cells is suggested. 3. Low-sodium Ringer perfusate augmented Na+ influx; in one group of gills the transport rate was more than double that of NaCl Ringer controls. The increase in transport induced by internal NH4+ was not additive with the low sodium augmentation. A reduction in intracellular (Na+) is postulated as the mechanism operating in both cases. 4. Ouabain had no appreciable effect on Na+ influx, either with or without NH4+ in the perfusate. Diamox partially blocked the augmented Na+ influx induced by NH4+. Amiloride completely inhibited Na+ influx, both with and without NH4+ in the perfusate.     

Mechanism of garlic (Allium sativum) induced reduction of hypertension in 2K-1C rats: a possible mediation of Na/H exchanger isoform-1

Garlic causes reduction in blood pressure (BP), however the role of Na/H exchanger (NHE) which mediates hypertension and related tissue-damage is poorly understood. In this study the effect of an established dose of raw garlic extract was investigated on the expression of NHE-1 and -3 and sodium pump activity in a 2K-1C model of hypertension in rats. 2K-1C animals showed high BP, increased serum concentration of PGE2 and TxB2, hypertrophy of the unclipped kidneys, but not in the clipped kidneys In addition, NHE-1 and NHE-3 isoforms were increased in both the 2K-1C kidneys, whereas alpha-actin was increased in the clipped but not in unclipped kidneys. Sodium pump activity was decreased in the clipped kidneys, but remained unchanged in the unclipped kidneys. Garlic treatment reduced the induction of NHE-1 only in the unclipped 2K-1C kidneys, whereas garlic treatment increased the sodium pump activity in both the 2K-1C kidneys. These findings demonstrate that the antihypertensive action of garlic is associated with a reversal of NHE-1 induction in the unclipped kidneys. Induction of NHE isoforms together with a reduced sodium pump activity might cause necrosis in the 2K-1C clipped kidneys due to cellular retention of Na+. On the other hand, activation of sodium pump by garlic extract in the kidneys should reduce intracellular Na+ concentration and normalize BP. These findings signify the use of garlic in the treatment of hypertension.     

Synergistic activation of ENaC by three membrane-bound channel-activating serine proteases (mCAP1, mCAP2, and mCAP3) and serum- and glucocorticoid-regulated kinase (Sgk1) in Xenopus Oocytes

Sodium balance is maintained by the precise regulation of the activity of the epithelial sodium channel (ENaC) in the kidney. We have recently reported an extracellular activation of ENaC-mediated sodium transport (I(Na)) by a GPI-anchored serine protease (mouse channel-activating protein, mCAP1) that was isolated from a cortical collecting duct cell line derived from mouse kidney. In the present study, we have identified two additional membrane-bound serine proteases (mCAP2 and mCAP3) that are expressed in the same cell line. We show that each of these proteases is able to increase I(Na) 6-10-fold in the Xenopus oocyte expression system. I(Na) and the number (N) of channels expressed at the cell surface (measured by binding of a FLAG monoclonal I(125)-radioiodinated antibody) were measured in the same oocyte. Using this assay, we show that mCAP1 increases I(Na) 10-fold (P < 0.001) but N remained unchanged (P = 0.9), indicating that mCAP1 regulates ENaC activity by increasing its average open probability of the whole cell (wcP(o)). The serum- and glucocorticoid-regulated kinase (Sgk1) involved in the aldosterone-dependent signaling cascade enhances I(Na) by 2.5-fold (P < 0.001) and N by 1.6-fold (P < 0.001), indicating a dual effect on N and wcP(o). Compared with Sgk1 alone, coexpression of Sgk1 with mCAP1 leads to a ninefold increase in I(Na) (P < 0.001) and 1.3-fold in N (P < 0.02). Similar results were observed for mCAP2 and mCAP3. The synergism between CAPs and Sgk1 on I(Na) was always more than additive, indicating a true potentiation. The synergistic effect of the two activation pathways allows a large dynamic range for ENaC-mediated sodium regulation crucial for a tight control of sodium homeostasis.     

Contribution of NaCl excretion to salt resistance of Aeluropus littoralis (Willd) Parl

Aeluropus littoralis is a perennial halophyte, native to coastal zones. Although it is usually exposed to high saline, this plant grows normally without toxicity symptoms. In order to assess leaf salt excretion, different growth parameters, Na(+), K(+), Ca(2+), Mg(2+) and Cl(-) concentrations, as well as excreted ions were examined in plants grown for 2 months in the presence of various salinity levels (0-800 mM NaCl). In addition, salt crystals, salt glands and other leaf epidermal structures were investigated. Results showed that total plant growth decreased linearly with increase to medium salinity. This reduction concerns mainly shoot growth. In addition, this species was able to maintain its shoot water content at nearly 50% of the control even when subjected to 800 mM NaCl. Root water content seemed to be unaffected by salt. Sodium and chloride ion contents in shoots and in roots increased with salinity concentrations, in contrast to our observation for potassium. However, calcium and magnesium contents were not greatly affected by salinity. Excreted salts in A. littoralis leaves were in favor of sodium and chloride, but against potassium, calcium and magnesium which were retained in plants. Sodium and chloride were excreted from special salt glands, which were scattered on the both leaf surfaces. In addition to salt glands, papillae were the most frequent epidermal structure found on A. littoralis leaves, and are likely involved in A. littoralis salt resistance.