scholarly journals Nonelectrolyte Penetration and Sodium Fluxes through the Axolemma of Resting and Stimulated Medium Sized Axons of the Squid Doryteuthis plei

1966 ◽  
Vol 50 (1) ◽  
pp. 43-59 ◽  
Author(s):  
Raimundo Villegas ◽  
Gloria M. Villegas ◽  
Margarita Blei ◽  
Francisco C. Herrera ◽  
Jorge Villegas
Keyword(s):  
Sodium Concentration ◽  
Ionic Species ◽  
The Other ◽  
Sodium Ions ◽  
Drag Effect ◽  
Sodium Influx ◽  
Low Sodium ◽  
External Potassium ◽  
Independent Effects ◽  
Extracellular Sodium

The penetration of 14C-labeled erythritol, mannitol, and sucrose through the axolemma was determined in medium sized paired axons, one at rest and the other stimulated 25 times per sec. The resting permeabilities, in 10-7 cm/sec, are erythritol, 2.9 ± 0.3 (mean ± SEM); mannitol, 2.3 ± 0.4; and sucrose 0.9 ± 0.1. In the stimulated axons they are: erythritol, 5.2 ± 0.3; mannitol, 4.0 ± 0.5; and sucrose, 1.8 ± 0.3. Thus, the calculated permeabilities during activity (1 msec per impulse), in the same units, are: 100, 75, and 38, respectively. These changes in permeability are reversible. The effects of external potassium and sodium concentrations on erythritol penetration were also studied. At rest, erythritol penetration is independent of potassium and sodium concentrations. In the stimulated axons, erythritol penetration decreases when the extracellular sodium is diminished. Sodium influx (not the efflux) decreases during rest and activity when the extracellular sodium is diminished. The diminution during activity of erythritol and sodium entries in low sodium solutions may be related to a decrease of a drag effect of sodium ions on the nonelectrolyte molecules or to independent effects of the sodium concentration on sodium influx and the nonelectrolyte pathways. The axolemma discriminates among erythritol, mannitol, sucrose, and the different ionic species during rest and activity.

The change from symmetry to asymmetry of a sodium transport system in red cell membranes

1985 ◽  
Vol 223 (1233) ◽  
pp. 449-457 ◽  
Keyword(s):  
Sodium Concentration ◽  
Tracer Studies ◽  
Chloride Medium ◽  
Sodium Influx ◽  
Nitrate Medium ◽  
Sodium Efflux ◽  
External Potassium ◽  
Red Cell Membranes ◽  
Stimulation Of ◽  
Human Red Cells

A study has been made with human red cells of sodium movements that are sensitive to the drug furosemide. The aim was to see if furosemide-sensitive movements that are symmetrical (exchange) became asymmetrical (net transport) on replacement of chloride with nitrate as the major external anion. Cells were incubated for 4 h at 37 °C with 140 mm sodium, and chloride or nitrate as the principal anion. Under a variety of conditions (presence and absence of ouabain or furosemide, or both) the cell sodium concentration was always higher when chloride was replaced with nitrate. The cells became leakier to sodium. Tracer studies indicated that, in contrast to the results in chloride medium, the decrease in sodium influx was greater than the fall in efflux when furosemide was added to cells in nitrate medium. The results confirm that the sensitivity of sodium efflux to furosemide depended on chloride. However, influx showed a different sensitivity in that furosemide still inhibited in cells incubated in nitrate medium. The stimulation of sodium influx with nitrate medium was independent of external potassium (10–50 mm) and the furosemide-sensitive influx was also constant. It is concluded that symmetrical transmembrane sodium movements with cells in chloride medium became downhill asymmetrical in nitrate medium, giving a net gain of cell sodium that was insensitive to ouabain and sensitive to furosemide. The drug thus partly retarded the gain of cell sodium that otherwise occurred in the somewhat leaky cells.

Extracellular Calcium, Magnesium, and Sodium Ion Competition in the Conductance Control of the Photosensory Membrane of Limulus Ventral Nerve Photoreceptor

1978 ◽  
Vol 33 (7-8) ◽  
pp. 574-579 ◽  
Author(s):  
H. Stieve ◽  
M. Bruns
Keyword(s):  
Membrane Potential ◽  
Calcium Concentration ◽  
Sodium Concentration ◽  
Extracellular Calcium ◽  
Magnesium Concentration ◽  
Sodium Ions ◽  
Extracellular Calcium Concentration ◽  
Calcium Magnesium ◽  
Extracellular Sodium ◽  
Ventral Nerve Photoreceptor

Abstract The membrane potential in the dark and the saturated response height of the ventral nerve photoreceptor of Limulus was measured by an intracellular electrode while the external concentration of calcium, magnesium and sodium ions was varied. Decreasing the extracellular calcium concentration from 10-2 mol/l causes a calcium-dependent lowering of the dark membrane potential and at very low concentrations (<10-8 mol/l a reversal to ca. +5 to +11 mV, if the external magnesium concentration is also low. Also, the light response diminishes with decreasing extracellular calcium concentration and disappears at a concentration of 10-9 mol/l. External magnesium can substitute for certain properties of extracellular calcium. Lowering the extracellular sodium concentration from 543 mmol/l to 30 - 50 mmol/1 reduces the dark membrane potential and the light responses at normal calcium concentration, whereas at low calcium concentration it causes a substantial rise of both. Interpretation: The results are in accordance with our working hypothesis that a strong reduction of the external calcium (and magnesium) concentration causes a calcium concentration dependent opening of “ light channels” in the dark. Additional lowering the extracellular sodium concentration counteracts this effect; opening and closing of light channels is controlled by negative binding sites on the cell membrane for which calcium and sodium ions compete with an antagonistic action.

Mechanism of Inhibition of Smooth Muscle Tension in Guinea-Pig Taenia Coli by Ouabain

1974 ◽  
Vol 52 (4) ◽  
pp. 898-901 ◽  
Author(s):  
D. Bose
Keyword(s):  
Guinea Pig ◽  
Muscle Tension ◽  
Sodium Concentration ◽  
Inhibitory Response ◽  
The Other ◽  
Extracellular Potassium ◽  
Taenia Coli ◽  
Mechanism Of Inhibition ◽  
Intracellular Sodium Concentration ◽  
Extracellular Sodium

Ouabain produced an increase in tension in the guinea-pig taenia coli which was abolished in the presence of high extracellular potassium. On the other hand the delayed inhibitory response of ouabain could only be abolished by the removal of extracellular sodium. The mechanism of inhibition of contraction by ouabain appears to be due to elevation of intracellular sodium concentration.

scholarly journals Strophanthidin-Sensitive Components of Potassium and Sodium Movements in Skeletal Muscle As Influenced by the Internal Sodium Concentration

1968 ◽  
Vol 52 (3) ◽  
pp. 389-407 ◽  
Author(s):  
R. A. Sjodin ◽  
L. A. Beaugé
Keyword(s):  
Sodium Concentration ◽  
Ringer Solution ◽  
Intracellular Sodium ◽  
Sodium Ions ◽  
Potassium Efflux ◽  
Sodium Efflux ◽  
High Sodium ◽  
Ringer’S Solution ◽  
Low Sodium ◽  
Potassium Influx

"Low sodium" muscles were prepared which contained around 5 mmoles/kg fiber of intracellular sodium. "High sodium" muscles containing between 15 and 30 mmoles/kg fiber of intracellular sodium were also prepared. In low sodium muscles application of 10-5 M strophanthidin reduced potassium influx by about 5%. Potassium efflux was unaffected by strophanthidin under these conditions. In high sodium muscles, 10-5 M strophanthidin reduced potassium influx by 45% and increased potassium efflux by 70%, on the average. In low sodium muscles sodium efflux was reduced by 25% during application of 10-5 M strophanthidin while in high sodium muscles similarly treated, sodium efflux was reduced by about 60%. Low sodium muscles showed a large reduction in sodium efflux when sodium ions in the Ringer solution were replaced by lithium ions. The average reduction in sodium efflux was 4.5-fold. Of the amount of sodium efflux remaining in lithium. Ringer's solution, 40% could be inhibited by application of 10-5 M strophanthidin. The total sodium efflux from low sodium muscles exposed to Ringer's solution in which lithium had been substituted for sodium ions for a period of 1 hr can be fractionated as 78% Na-for-Na interchange, 10% strophanthidin-sensitive sodium pump, and 12% residual sodium efflux. It is concluded that large strophanthidin-sensitive components of sodium and potassium flux can be expected only at elevated sodium concentrations within the muscle cells.

Sodium Regulation in the Crayfish Astacus Fluviatilis

1960 ◽  
Vol 37 (1) ◽  
pp. 100-112
Author(s):  
G. W. BRYAN
Keyword(s):  
Tap Water ◽  
Sodium Concentration ◽  
The Body ◽  
Distilled Water ◽  
Sodium Influx ◽  
Low Sodium ◽  
Diffusion Component ◽  
Suitable Site ◽  
Astacus Fluviatilis ◽  
Sodium Regulation

1. In distilled water or artificial tap water with a very low sodium concentration, sodium uptake by Astacus is prevented or reduced and 22Na outflux is subnormal. This is accounted for to only a small extent by reduced renal sodium losses. 2. Sodium-depleted animals replaced in artificial tap water regain sodium in a roughly exponential manner. This is shown by 22Na to be the result of a considerable increase in sodium influx coupled with an increased but lower outflux. 3. Sodium outfiux appears to consist of three components: urine losses, passive diffusion losses over the body surface and what may be an ‘exchange diffusion’ component which is high during high influx and minimal in distilled water. This latter component represents about 30% of sodium exchange under normal conditions. 4. Eyestalk removal did not affect the ability of Astacus to absorb sodium. 5. In starved animals the gills take up most of the sodium absorbed and the gut is relatively unimportant. 6. Silver staining of the gills is a passive process and the cuticle of the branchial filaments of the gill stem is selectively stained. This region would be a suitable site for ion uptake mechanisms.

The Absorption of Sodium Ions by the Crayfish, Astacus Pallipes Lereboullet

1959 ◽  
Vol 36 (1) ◽  
pp. 126-144 ◽  
Author(s):  
J. SHAW
Keyword(s):  
Uptake Rate ◽  
Equilibrium Concentration ◽  
Maximum Level ◽  
Sodium Concentration ◽  
Sodium Content ◽  
Sodium Balance ◽  
Sodium Ions ◽  
External Concentration ◽  
Sodium Influx ◽  
True Measure

1. The effects of external and internal sodium concentrations on the uptake of sodium ions by the crayfish, Astacus pallipes, has been studied. 2. The normal sodium influx, measured with 24Na, from O.3 mM /l. NaCl solution is 1.5 µM./10 g. body weight/hr. The rate of loss of sodium to de-ionized water has roughly the same value. 3. Net loss of sodium reduces the external sodium concentration required for sodium balance. The minimum equilibrium concentration is about 0.04 mM./l. NaCl. 4. The relation between the external sodium concentration and the sodium influx is non-linear. The influx has a maximum of about 10 µM./10 g./hr. at an external concentration of approx. 1 mM./l. 5. The 24Na influx is a true measure of the sodium uptake rate at low external concentrations. At higher concentrations the influx may exceed the uptake rate by some 20%. 6. Net loss of sodium increases the influx by three to five times. Loss of 5-10% of the total internal sodium increases the influx from the normal to the maximum level. A 1% change has a significant effect on the influx. Changes in the internal sodium content reflect changes of the blood sodium concentration. 7. A scheme is suggested whereby the external and internal sodium concentrations interact together on the influx to produce a self-regulating system which maintains the animal in sodium balance.

Sodium Influx and Loss in Freshwater and Brackish-Water Populations of the Amphipod Gammarus Duebeni Lilljeborg

1971 ◽  
Vol 54 (1) ◽  
pp. 255-268
Author(s):  
D. W. SUTCLIFFE
Keyword(s):  
Body Surface ◽  
Brackish Water ◽  
Sea Water ◽  
Sodium Concentration ◽  
The Body ◽  
Experimental Population ◽  
Sodium Ions ◽  
Sodium Influx ◽  
Wide Range ◽  
Freshwater Habitats

1. Sodium influx was examined in Gammarus duebeni from freshwater habitats on the Kintyre and Stranraer peninsulas in western Britain, and from a brackish-water habitat in Ireland. The affinity for sodium ions in the uptake mechanism at the body surface was similar in animals from the three localities. 2. Compared with the parent population from Kintyre, an experimental population established for 2 years in water with a lower sodium concentration showed an increased affinity for sodium. 3. Sodium losses in the urine of animals from the above localities were negligible at external salinities below about 2% sea water. In contrast, urinary sodium losses in animals from a brackish-water population in Britain were higher at salinities ranging from 40% sea water to well below 2% sea water. 4. The affinity for sodium ions in uptake mechanisms at the body surface and in the antennary glands of G. duebeni from a wide range of habitats shows a market correlation with the sodium concentration of the habitat. The permeability of the body surface to outward movement of sodium is similar in G. duebeni from brackishwater and freshwater habitats. 5. It is suggested that most of the observed physiological differences between populations of G. duebeni are phenotypic in origin. The status of the freshwater ‘race’ in Ireland is briefly discussed.

Changes of sodium transport in erythrocytes of the maturing rabbit

1975 ◽  
Vol 228 (2) ◽  
pp. 461-464 ◽  
Author(s):  
EK Smith ◽  
L Weihrauch ◽  
D Farrington
Keyword(s):  
Atpase Activity ◽  
Sodium Transport ◽  
Sodium Concentration ◽  
Red Cells ◽  
Potassium Content ◽  
High Potassium ◽  
Sodium Influx ◽  
Sodium Efflux ◽  
Low Sodium ◽  
Total Sodium

The red blood cells of New Zealand white rabbits have a low sodium and high potassium content. As the animals mature, the sodium concentration rises and the potassium content falls; studies of red cells from a group of five young and five mature animals revealed a highly significant increase of cell sodium with age that was associated with a significant fall in the rate of ouabain-inhibited active sodium efflux. This difference was still seen when the sodium concentration within the cells from old and young animals was equalized and elevated to saturating levels for active pump efflux. Total sodium efflux, however, increased significantly with age as did total sodium influx so that a steady state was reached. Ouabain-sensitive ATPase activity fell significantly in the cell membranes from older animals and ouabain-insensitive ATPase increased with age. The survival time of 51Cr-labeled red cells was significantly longer in old than in young animals and it is concluded that as the rabbit matures its red cells survive for a longer period and this is associated with the changes of sodium transport and ATPase activity that have been documented.

Effects Of Altered pH And Sodium Concentration On The Response Of Megakaryocytes And Platelets To ADP

1981 ◽  
Author(s):  
R M Leven ◽  
V T Nachmias
Keyword(s):  
Platelet Rich Plasma ◽  
Shape Change ◽  
Gel Filtration ◽  
Adenosine Monophosphate ◽  
Adenosine Diphosphate ◽  
Sodium Concentration ◽  
Sodium Influx ◽  
A 23187 ◽  
Ruffled Border ◽  
Extracellular Sodium

By using both megakaryocytes and platelets to study effects of adenosine diphosphate (ADP), we hope to understand the ionic events underlying the shape changes induced by this nucleotide. Guinea pig bone marrow megakaryocytes were isolated to 50-90% purity by modifications of published procedures, and cultured for 12-48 hours. In response to ADP (l-10μM) megakaryocytes develop a ruffled border and spread in 15-30 minutes to 2-3 times their original diameter and adhere strongly to the substrate. Several other diphosphonuc1eotides or adenosine monophosphate have no effect. Spreading occurs in calciummagnesium free Hank’s salt solution, but is blocked when extracellular sodium was replaced by potassium, choline, or lithium. Amiloride, an inhibitor of sodium uptake, inhibits the extent of spreading 90% at 10-4M, but allows partial spreading in 60% of the cells. Spreading can be mimicked by incubating the cells with 2μM A-23187 combined with either 5mM methylamine or 1μM monensin, but not by A-23187 alone.The rate of platelet shape change was measured spectro- photometrical1y at 37°C with 5mM EGTA both in platelet rich plasma (PRP) or after gel filtration in phosphate buffered saline. Amiloride inhibits shape change completely at 1mM and 50-60% at 0.1mM, but only if present during gel filtration. A rapid drop in buffer pH from 7.4 to 6.9 causes a 50% inhibition of rate of shape change in PRP or after gel filtration, but the inhibition spontaneously reverses within three minutes incubation at the lower pH.These results are compatible with a model in which ADP causes a sodium influx which is linked to a change in intracellular pH. This may be a necessary but not necessarily sufficient step in ADP induced shape change.

scholarly journals Weighing the prognostic role of hyponatremia in hospitalized patients with metastatic solid tumors: the HYPNOSIS study

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Giovanni Fucà ◽  
Luigi Mariani ◽  
Salvatore Lo Vullo ◽  
Giulia Galli ◽  
Rossana Berardi ◽  
...  
Keyword(s):  
Solid Tumors ◽  
Serum Sodium ◽  
Tumor Development ◽  
Sodium Concentration ◽  
Prognostic Impact ◽  
Multivariable Model ◽  
Low Sodium ◽  
Extracellular Sodium

Abstract Previous works linked low sodium concentration with mortality risk in cancer. We aimed at weighing the prognostic impact of hyponatremia in all consecutive patients with metastatic solid tumors admitted in a two-years period at our medical oncology department. Patients were included in two cohorts based on serum sodium concentration on admission. A total of 1025 patients were included, of whom 279 (27.2%) were found to be hyponatremic. The highest prevalence of hyponatremia was observed in biliary tract (51%), prostate (45%) and small-cell lung cancer (38.9%). With a median follow-up of 26.9 months, median OS was 2 months and 13.2 months for the hyponatremia versus control cohort, respectively (HR, 2.65; P < 0.001). In the multivariable model, hyponatremia was independently associated with poorer OS (HR, 1.66; P < 0.001). According to the multivariable model, a nomogram system was developed and validated in an external set of patients. We weighed over time the influence of hyponatremia on survival of patients with metastatic solid tumors and pointed out the possibility to exploit serum sodium assessment to design integrated prognostic tools. Our study also highlights the need for a deeper characterization of the biological role of extracellular sodium levels in tumor development and progression.

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