Sodium Outflux Research Articles

Effect of low pH on sodium regulation in two species of Daphnia

The effect of low pH on sodium-22 influx and outflux of Daphnia magna and Daphnia middendorffiana was assessed. Experiments were conducted in both hard and soft water with experimental pHs ranging from 3.5 to 8.0. In hard water, at and below pH 4.0, there was a net loss of sodium from both species. The rate of sodium loss (outflux) increased significantly, while the rate of uptake (influx) remained constant at pH 4.0 compared with the reference pH 8.0. Only at extremely low pH (pH 3.5) was sodium influx inhibited in hard water. In soft water, D. magna responded quite differently. Sodium influx was inhibited by 23% at pH 5.0 and by 69% at pH 4.5 compared with the control (pH 6.5). Sodium outflux was stimulated to 125% of the control at pH 4.5. The net loss of sodium in soft water was due to both an increase in sodium outflux and a decrease in sodium influx, while in hard water the effect was primarily on sodium outflux. Daphnia magna and D. middendorffiana have problems with sodium regulation below pH 5.5 in soft water and below pH 4.5 in hard water, which indicates that they are considerably more sensitive to low pH in soft water than in hard water.

Sodium outflux and influx within nerve terminals from chronic epileptogenic foci

The Na +-pump ( 0M Na p) or maximal sodium outflux inhibited by ouabain was studied in nerve terminals isolated from the primary and mirror epileptogenic foci of freezing lesions. In addition, the Na + for Na + exchange diffusion that is sensitive to ethacrynic acid and furosemide was also analyzed. 0M Na p in control and epileptogenic states had similar and indistinguishable activation curves for K 0 (extracellular K) in a sodium medium except for a two-fold difference in magnitude. However, the apparent affinity of the Na +-pump for K 0 as measured byK 1/2 was shifted to the right or decreased in epileptogenic foci (2 mM K 0 compared to 0.5 mM in controls) when measured in a magnesium medium. A decrease in the apparent affinity for internal sodium was also observed. Of the total sodium outflux (67.7 nmol/mg/min), Na + movements which are insensitive to ouabain and external K + but stimulated by external Na + and inhibited by furosemide and ethacrynic acid (20 nmol/mg/min or 32% of sodium outflux) represented the Na + for Na + exchange diffusion in nerve terminals. Na + influx rising with increasing internal sodium in the presence of ouabain and blocked by furosemide represent the corresponding inward Na + movement. No differences were observed between controls and epileptogenic states.

The sodium pump of erythrocytes from patients with Duchenne muscular dystrophy: effect of ouabain on the active sodium flux and on (Na+, K+)ATPase.

Active ion exchanges across erythrocyte membrane from patients with Duchenne muscular dystrophy were studied by two methods: --erythrocyte ghosts (Na+,K+)ATPase activity and its sensibility to ouabain, using an enzymatic method; --active sodium outflux and its sensibility to ouabain using a radioisotopic method. (Na+,K+)ATPase activity and active sodium outflux were decreased in dystrophic patients compared to normal sex- and age-matched controls. Enzymatic activity and active sodium outflux were inhibited by ouabain 10(-4) M in patients and in controls. Inhibition of the active sodium outflux was lower in patients than in controls. The results are discussed in light of the literature.

The effect of ethanol on ion transport in frog skin

Frog skin has been used as a model epithelial sodium-transporting system to study the effect of ethanol on ion transport. Treatment of the outside of frog skin with ethanol decreased the net sodium transport due to inhibition of 22Na + influx. Ethanol did not alter sodium outflux when bathing the outside of the skin. The inhibition was in proportion to the concentration of ethanol, 0.25 M resulting in 50% inhibition. The chloride permeability of the skin was increased several-fold when the skin was exposed to ethanol in either bathing solution. With 0.4 M ethanol in the inner bathing solution, all the unidirectional fluxes of Na + and Cl − were increased. The movement of Cl − was evaluated by comparison of Cl − flux with urea flux, since urea is thought to move passively across frog skin via an extracellular (shunt) pathway. Chloride flux was increased to a greater extent than urea flux. These experiments indicate that ethanol affects chloride permeability beyond an increase in extracellular ion flow and independent of its effect on Na + transport.

Pathways for chloride and sodium transport across toad skin.

The voltage dependecies of Na and Cl fluxes were investigated in the isolated toad skin. With Cl-Ringer's on both sides Cl outflux varied very little with clamping voltage. The same was true for the influx of Cl at depolarizing voltages (psii -psio lessthan0 mV), wheras hyperpolarization led to a marked increase in this flux. A net chloride influx under short circuit conditions indicated active transport of chloride. The outflux of Cl was a saturable function of outside Cl concentration. The outflux of urea was hardly affected by raising outside Cl concentration, and the effect of varying outside nitrate concentration on Cl outflux was likewise small. Both influx and outflux could be inhibited partially bt acetazolamide. The outflux of Na varied with the clamping voltage as would be expected for an ion transported by electrodiffusion, and it was shown that amiloride had no effect on Na outflux, so it was concluded that the Na outflux route is particular. In the absence of Cl in the outside solution a small outflux of Cl persists. Also this flux varied with the clamping voltage according to laws for electrodiffusion. The variation of the ratio of sodium outflux to chloride outflux with clamping voltage indicated free passive diffusion of both these ions under the conditions mentioned. A comparison of the outfluxes of Na and Cl in skins bathed with gluconate Ringer's outside showed that the outflux route of these two ions was cation selective (PNa/PCl=1.88). When the paracellular leak pathway of the skins was opened by exposing the outside to hyperosmolar urea solutions, the ratio of the transport numbers was found to be TNa/TCl=1.71. The roles of the two ions in determining the steady state current-voltage relationships were compared. At hyperpolarizing voltages most or all of the clamping current was carried by an inward Cl flux. By depolarization sodium influx plays an increasing role with increasing depolarization. Under short circuit conditions active chloride transport was found to contribute to the short circuit current.

Effects of extracellular cations and ouabain on catecholamine-stimulated sodium and potassium fluxes in turkey erythrocytes.

In turkey erythrocytes, potassium influx can be inhibited by several cations whose order of effectiveness is Rb greater than Cs greater than Li greater than Mg = Ca = Ba. Extracellular sodium does not alter potassium influx. Sodium influx is not altered by any of these monovalent cations but magnesium, calcium, or barium reduced sodium influx by 30 to 40%. Potassium outflux is not influenced by extracellular sodium or potassium while sodium outflux is not influenced by extracellular potassium but increases progressively with increasing extracellular sodium. Isoproterenol stimulates potassium influx only when sodium or lithium is present in the medium and catecholamine stimulation increases progressively with increasing extracellular sodium. Isoproterenol-stimulated sodium influx is enhanced by extracellular potassium, rubidium or cesium, and catecholamine stimulation increases progressively with increasing extracellular potassium. Isoproterenol inhibits potassium outflux in a solution free of sodium and potassium, and this inhibition can be abolished by adding sodium but not by adding potassium. In solutions containing both sodium and potassium, isoproterenol stimulates potassium outflux, and this stimulation increases progressively with increasing extracellular sodium or potassium. Isoproterenol-stimulated sodium outflux is not influenced by extracellular sodium or potassium. Isoproterenol-stimulated cellular cyclic adenosine 3':5'-monophosphate (cyclic AMP) is reduced slightly (25%) by removing extracellular sodium and potassium from the incubation solution, but this effect is not of sufficient magnitude to account for the effects of these cations on isoproterenol-stimulated cation transport. Ouabain does not alter the effect of extracellular sodium or potassium on isoproterenol-stimulated potassium influx; however, the glycoside potentiates (by 20 to 40%) the effects of these two cations on isoproterenol-stimulated sodium influx. Ouabain does not alter potassium outflux when the incubation solution contains both sodium and potassium; however, ouabain stimulates potassium outflux in an incubation solution free of sodium or potassium.

Refractoriness of cation transport in turkey erythrocytes to stimulation by cyclic adenosine 3':5'-monophosphate.

In turkey erythrocytes bidirectional fluxes of sodium and potassium develop a time-dependent refractoriness to stimulation by endogenous cyclic adenosine 3':5'-monophosphate (cyclic AMP). The refractoriness of potassium influx and potassium outflux (both of which require extracellular sodium and potassium for stimulation by cyclic AMP) depends on the extracellular concentrations of sodium and potassium. In contrast, the refractoriness developed by sodium outflux (which does not require extracellular sodium or potassium for stimulation by cyclic AMP) does not depend on the extracellular concentrations of sodium or potassium. The refractoriness of these fluxes to cellular cyclic AMP reflects a decrease in the amount by which they can be maximally stimulated and appears to be proportional to the extent to which the transport system is utilized during the course of the incubation. Ouabain significantly reduces the rate at which cation transport in turkey erythrocytes becomes refractory to endogenous cyclic AMP. This effect of the glycoside is independent of the extracellular concentrations of sodium or potassium and does not correlate with how it alters the initial response of the transport systems to cyclic AMP.

Studies on active and passive cation fluxes in congenital hemolytic anemia with high sodium and low potassium erythrocytes

A six year old girl suffering from severe nonspherocytic hemolytic anemia which was characterized by Stomatocytosis, macrocytosis, and autohemolysis type I was found to have erythrocytes with reduced potassium (16 mval/l) and elevated sodium (95 mval/1; concentrations. Glykolysis, ATP formation and ATP utilization of the cells were markedly increased. Active sodium outflux and potassium influx were increased ten- and six fold, respectively. Inhibition of the cation pump by ouabain decreased the active cation fluxes for about 60 %. Passive sodium and potassium fluxes were likewise markedly increased. Normal red cells reconstituted with intracellular cation concentrations which were similar to the concentrations of the abnormal cells showed only a slight increase of active cation fluxes. The results suggest a defect of passive cation permeability of the abnormal cells.

Effects of Ouabain on Catecholamine-stimulated Sodium Transport in Turkey Erythrocytes

Abstract In intact turkey erythrocytes ouabain, a specific inhibitor of sodium- and potassium-dependent ATPase, inhibits fractional sodium outflux but does not alter sodium influx. Ouabain increases isoproterenol-stimulated sodium influx by 50%, decreases isoproterenol-stimulated sodium outflux by 20%, but does not alter either the minimally effective concentration of isoproterenol (10-9 m) or the concentration (10-7 m) required for maximal stimulation of sodium fluxes. The glycoside also prolongs the duration of catecholaminestimulated sodium transport but has no effect on either the magnitude or the time course of catecholamine-stimulated cellular accumulation of cyclic 3' : 5'-AMP. This ability of ouabain to relieve the refractoriness of turkey erythrocytes to endogenous cyclic 3' : 5'-AMP suggests that the mechanisms through which ouabain and the cyclic nucleotide exert their effects may at some point share a common biochemical pathway.

Factors affecting the net fluxes of ions in the isolated perfused gills of freshwaterAnguilla dieffenbachii

The net fluxes of sodium, chloride and potassium across the gills of freshwaterAnguilla dieffenbachii were measured using an isolated, perfused preparation. Reductions in the external sodium and chloride concentrations below 1.0 mMol/l resulted in an increasing net outflux of these ions from the gill (Fig. 1) whereas reductions in the internal sodium and chloride concentrations had no significant effect on the net fluxes of these ions (Fig. 2). Increases in the internal sodium and chloride concentrations above those normally found in the serum resulted in increasing net outfluxes of these ions (Fig. 2). Reductions in the internal potassium concentration below 1.0 mMol/l resulted in an increasing net outflux of sodium essentially similar to that obtained on reducing the external sodium concentration (Fig. 3). These results are discussed with reference to the possible active transport of ions across the branchial epithelium of teleosts in fresh water. In particular, the involvement of Na+/K+ exchanges in such transport processes are considered.

Effect of β-Adrenergic Catecholamines on Sodium Transport in Turkey Erythrocytes

Abstract Sodium fluxes across the plasma membrane of turkey erythrocytes are 2 to 3 times greater than corresponding fluxes in human erythrocytes. Extracellular potassium stimulates fractional sodium outflux and inhibits sodium influx in turkey erythrocytes. In contrast to human erythrocytes, turkey erythrocytes showed no evidence for sodium-sodium exchange, and at all sodium concentrations studied addition of extracellular potassium inhibited sodium influx. Isoproterenol stimulated accumulation of cyclic adenosine 3':5'-monophosphate (cyclic 3':5'-AMP) and produced a 2- to 4-fold increase in sodium fluxes in turkey erythrocytes. The potency of catecholamine analogs for stimulation of sodium transport correlated directly with their potency for activation of adenylate cyclase in the turkey erythrocyte membrane. Stimulation of sodium transport by isoproterenol is reproduced by adding cyclic 3':5'-AMP to the medium and is blocked by propranolol. The increase in cyclic 3':5'-AMP in response to isoproterenol progresses unimpaired for at least 2 hours. The increase in sodium transport, however, begins to diminish within 30 min after addition of isoproterenol, and after 3 hours of incubation sodium fluxes are only slightly greater than for the control. This phenomenon presumably reflects accumulation of an inhibitor or depletion of a necessary factor for the transport system activated by intracellular cyclic 3':5'-AMP. The rapid effect described here of catecholamines on sodium transport as well as certain results with other systems controlled by hormones through cyclic 3':5'-AMP suggest that endocrine regulation of sodium transport is of general biological significance.

Competitive role of calcium in sodium transport in the crab carcinus mediterraneus Acclimated to low salinities

Influence of calcium on sodium fluxes was investigated in the brackish-water crab Carcinus mediterraneus Csrn., after activation of sodium regulatory mechanisms, during longterm acclimation in diluted (15.9 ‰ S) sea water. The 22Na outflux constants measured in whole crabs are noticeably lower (0.188 to 0.374h-1) in diluted sea water enriched by calcium (5.8 to 10.4 mM Ca2+/l), than in ordinary diluted sea water (0.545 h-1). The sodium-outflux constants in hemolymph, gills and muscle show the same trend of slower exchange of 22Na in calcium-enriched sea water. In ordinary sea water, the total sodium-outflux rate from the hemolymph amounts to 46.31 μM Na/g/h, while in calcium-enriched sea water (8.23 mM Ca2+/l) it is inhibited, amounting to 13.86 μM Na/g/h. Sodium and potassium concentrations of intracellular muscles in diluted sea water enriched with calcium and control diluted sea water are similar. The outflux of intracellular sodium from the muscle amounts to 2.84 μM Na/g/h in crabs acclimated to diluted sea water.

Studies on the permeability of human oral mucosa. VI. The mucosal transport of water, sodium and potassium under varying osmotic pressure.

The effect of osmotic pressure on the flow of water and on the flux of sodium and potassium through buccal and palatal mucosa has been investigated in 7 young adults by analysing the changes in weight and electrolyte content of solute-saturated discs of ash-free filter paper after mucosal contact. Solutions with an electrolyte content of 25 meq Na/1 and 25 meq K/1 and an osmolarity of 0.10—1.80 osmol/1 due to an increasing content of sucrose were employed. Linear relations between water transport and oral surface osmolarity were observed in both buccal and palatal mucosa. With solutions of low osmolarity an inflow was recorded, which gradually decreased and changed to outflow with increasing solute osmolarity. Isotony was recorded in buccal mucosa at 0.47 osmol/1 and in palatal mucosa at 1.09 osmol/1. A corresponding net flux of sodium and potassium was not registered under hypotonic and isotonic conditions. Under strong hypertony an outflux of sodium was observed from palatal mucosa as an atypical reaction in two of the persons. The observations indicated that there is no active transport of sodium through human keratinized and non-keratinized oral squamous epithelium.

The role of the gills in seawater adaptation inAnguilla dieffenbachii

Summary. Throughout the period of adaptation to sea water the net flux of potassium in the isolated gills remains constant. Initially on transfer to sea water a small net influx of sodium and chloride ions is recorded in the isolated gills. Within a short period of time a net outflux of sodium and chloride is recorded which progressively increases, reaching a maximum after approximately 100 hours of adaptation (Fig. 1). Despite unfavourable osmotic and ionic gradients the functioning of the isolated gill is such that the concentration of the fluid passing through it is actually reduced after some 10-15 hours of seawater adaptation (Fig. 2).

Evolution of the branchial sodium outflux and its components, especially the [formula omitted] exchange and the Na-K dependent ATPase activity during adaptation to sea water in Anguilla anguilla

1. 1. Branchial biochemical and functional readjustments in Anguilla anguilla were studied during 3 weeks following transfer to sea water. 2. 2. A rapid increase in plasma Na, total Na efflux and passive Na leak were observed attaining a maximum respectively in 2,4 and 7 days after transfer. Steady-state values were attained after 1–2 weeks' adaptation. 3. 3. The active extrusion mechanism ( Na K exchange flux) increased more slowly to attain a maximum 7–14 days after transfer. 4. 4. Na-K dependent ATPase (E.C. 3.6.1.4) activity varies in parallel to the Na K exchange. 5. 5. Seasonal variations in the pattern of readjustment were observed.

Impaired renal tubular secretion of potassium, elevated sweat sodium chloride concentration and plasma inhibition of erythrocyte sodium outflux as complications of systemic lupus erythematosus.

A 23-year-old male with systemic lupus erythematosus and hypocomplementemic glomerulonephritis (creatinine clearance 84 ml/min) developed severe hyperkalemia when given a normal sodium and potassium intake. Potassium excretion increased subnormally in response to ammonium chloride, sodium bicarbonate and a sodium-retaining steroid. Renal conservation of sodium and excretion of ammonium were impaired. These observations are consistent with defects in secretion of potassium and hydrogen ion by the distal tubule. Sodium transport by sweat ducts and normal erythrocytes incubated in the patient's plasma was impaired. The several abnormalities in ion transport could have been caused by a circulating substance(s), possibly acquired as a result of systemic lupus erythematosus.

Effects of hypophysectomy and prolactin on the sodium balance of Tilapia mossambica in fresh water

This work was undertaken to investigate the causes of the fall in plasma sodium levels seen in hypophysectomized Tilapia mossambica kept in fresh water, as well as also to study the mechanism of action of prolactin on such fish. Radioisotope techniques permitted simultaneous determination of branchial sodium influx and total (branchial and renal) sodium outflux. In intact Tilapia positive or steady state Na balance was attained only after 48 hr adaptation in the flux chambers. Before this time, the sodium outflux exceeds the influx, an effect presumably due to shock. Fish injected with saline were in negative sodium balance because of reduced influx and increased outflux. Hypophysectomized fish were in negative sodium balance irrespective of the time of adaptation in the chambers. Compared to intact fish, decreased Na influx and increased Na outflux were observed. Prolactin treatment of hypophysectomized fish restored the sodium balance of the fish by reducing the sodium outflux, although it did not bring Na influx back to normal. Saline-treated control fish remained in negative balance. These effects of hypophysectomy and of prolactin are thus similar to those observed in Fundulus heteroclitus and Poecilia latipinna.

Juvenile myeloid leukemia with fetal erythropoiesis.

A case of juvenile myeloid leukemia in a 21/2-year-old girl is described. Apart from the typical clinical features encountered, this case was characterized by a fetal pattern of erythropoiesis, with exceptionally high levels of fetal hemoglobin, up to 85%, associated with decreased levels of hemoglobin A2 and carbonic anhydrase. There was also a slight elevation of the sodium content and sodium outflux in the patient's red blood cells similar to that recorded in six newborn babies. Significance of these findings is discussed in relation to current concepts of type of erythropoiesis found in this form of leukemia.

Altered membrane sodium transport in Bartter's syndrome.

To explore the possibility that Bartter's syndrome is the manifestation of an inherited abnormality of sodium transport, we have measured various parameters of sodium transport in erythrocytes from patients with Bartter's syndrome, their siblings, and their parents. Sodium transport in six of the eight patients with Bartter's syndrome differed significantly from that in the other two patients. On the basis of this difference, the patients were divided into two groups (type I and type II). In the six type I patients, fractional sodium outflux (0.38+/-0.05/hr [SD]) was significantly less than normal (0.50+/-0.07) and erythrocyte sodium concentration (9.48+/-0.84 mmoles/liter cells per hr) was significantly greater than normal (5.24+/-0.66). In the two type II patients, none of the measured parameters of sodium transport differed significantly from normal. Erythrocyte sodium transport in the relatives of three type I patients was altered in a way similar to that in the type I patients and was significantly different from that in the relatives of a type II patient. These findings indicate the presence of inherited alterations of erythrocyte sodium transport in certain patients with Bartter's syndrome.

The effects of calcium on branchial sodium fluxes in the sea-water adapted eel, Anguilla anguilla, L.

1. The sodium influx through the gills of eels placed in calcium-free sea water for 15 hr was double that of controls. The effect was reversed in 1 hr by addition of calcium.2. The total sodium outflux through the gills of fish placed in calcium-free sea water for 15 hr was double that of controls. The effect was only partially reversed in 15 hr by addition of calcium.3. The passive outflux component of the total outflux was increased fourfold when calcium was removed and was restored to normal in 15 hr by addition of calcium. The active (exchange) outflux component of the total outflux was halved by calcium removal and increased above normal following calcium addition.4. The inability of calcium to restore the total outflux to normal within 15 hr in calcium-depleted fish, together with the raised plasma sodium concentration at this time, suggests that the raised outflux is caused by homoeostatic mechanisms, rather than permeability changes in the gill epithelium.