Rates of efflux and intracellular concentrations of potassium, sodium and chloride ions in isolated fat-cells from the rat

1. The metabolism of K(+), Na(+) and Cl(-) has been investigated in isolated fat-cells prepared from the epididymal adipose tissue of rats. 2. Methods are described for measuring the intracellular water space, the rates of loss of intracellular (42)K(+), (22)Na(+) and (36)Cl(-) and the intracellular concentrations of K(+), Na(+) and Cl(-) in isolated fat-cells. 3. The intracellular water space, measured as the [(3)H]water space minus the [carboxylic acid-(14)C]inulin space, was 3.93+/-0.38mul./100mg. cell dry wt. 4. The first-order rate constants for radioisotope effluxes from isolated fat-cells were 0.029min.(-1) for (42)K(+), 0.245min.(-1) for (22)Na(+) and 0.158min.(-1) for (36)Cl(-). 5. The intracellular concentrations of K(+), Na(+) and Cl(-) were 146m-equiv./l., 18.6+/-2.9m-equiv./l. and 43+/-2.4m-equiv./l. respectively. 6. The total intracellular K(+) content of isolated fat-cells was determined by atomic-absorption spectrophotometry to confirm the value obtained from the radioisotope-efflux data. 7. The ion effluxes from isolated fat-cells were: K(+), 1.5pmoles/cm.(2)/sec., Na(+), 1.6pmoles/cm.(2)/sec., and Cl(-), 2.4pmoles/cm.(2)/sec. 8. The membrane potential of isolated fat-cells calculated from the Cl(-) distribution ratio was -28.7mv.     

Salinity resistance in Zea mays: fluxes of potassium, sodium and chloride, cytoplasmic concentrations and microsomal membrane lipids

Abstract Cytoplasmic concentrations, fluxes of K⁺, Na⁺ and Cl and microsomal membrane lipids were investigated in a salt-sensitive and salt-resistant variety of Zea mays. The salt resistance of Protador relative to LG_H (salt-sensitive) appears to be related to higher K⁺ fluxes and cytoplasmic concentrations, and lower Na⁺ and Cl fluxes and cytoplasmic concentrations, when grown in NaCl. There were no apparent differences in the simple chemical composition of root microsomal membrane lipids between the two varicties, neither were these affected by salt.     

Plasma insulin concentrations during infusions of potassium and sodium chloride solutions into conscious splenectomized sheep

Haematocrit values, plasma osmolality and the plasma concentrations of sodium, potassium, chloride and insulin were measured in carotid arterial blood before, during and after intravenous infusion of NaCl (0.5 mol 1-1) and KCl (0.5 mol 1-1) at 2 ml min-1 for 105 min into six conscious splenectomized sheep. Hypertonic NaCl infusion was associated with a fall in haematocrit of 1.30 +/- 0.10% (P less than 0.001) and no consistent change in plasma insulin concentration occurred during this infusion. Hypertonic KCl infusion caused the haematocrit to increase by 1.70 +/- 0.39% (P less than 0.001) and the plasma insulin concentration to increase by 60.0 +/- 16.3 mu U ml-1 (P less than 0.01). It was concluded that this increase in insulin concentration was caused by elevation of the plasma potassium concentration and was not due to coincident increases in plasma chloride concentration or osmolality. Shrinkage of the extracellular fluid volume during KCl infusion made no major contribution to the increase in insulin concentration which was probably the result of increased release from the pancreas.     

The composition of animal cells: solutes contributing to osmotic pressure and charge balance

The cytoplasmic solutes of vertebrates and invertebrates, other than Na, K and Cl, are surveyed in relation to their influence on ionic regulation through osmolality and charge balance. The most abundant include MgATP, phosphagens, amino acids, various other nitrogen and phosphorus compounds and sometimes anaerobic end products and antifreeze agents. Differences in muscle osmolality, e.g. between marine and non-marine animals, affect mainly nitrogenous solutes of no net charge, such as certain amino acids, taurine, betaine, trimethylamine oxide and urea. The high osmolality of axoplasm in marine invertebrates is due more to anions such as aspartate, glutamate and isethionate.     

Effect of fluoride and other metabolic inhibitors on intracellular sodium and potassium concentrations in L cells

Fluoride, iodoacetate, oxamate, 2,4-dinitrophenol, cycloheximide, and ouabain were studied to determine if any of these inhibitors affected the intracellular concentration of sodium and potassium in an L cell strain of mouse fibroblasts and to determine if the changes observed in these parameters could be correlated with growth rate. The results indicated that (1) the intracellular concentration of sodium and potassium could not be correlated with growth rate, (2) fluoride, iodoacetate, oxamate, 2,4-dinitrophenol, and cycloheximide at concentrations having an equal effect on growth had a similar effect on the intracellular sodium and potassium concentration These changes were not as great as those seen with ouabain, which at a concentration which did not inhibit growth, had an equal or greater effect on the intracellular sodium and potassium concentration.     

Responses of alfalfa to potassium, calcium, and nitrogen under stress induced by sodium chloride

The physiological responses of alfalfa (Medicago sativa L. cv. Gilboa) to salinity (100 mM NaCl) and some inorganic nutrients (K+, Ca2+ and N as NO3-) were investigated. Salinity caused a substantial reduction in biomass, carbon assimilation rate, stomatal conductance, water use efficiency, leaf area, relative growth rate, NO3- content and nitrate reductase activity, whereas, transpiration rate was slightly affected. Inclusion of K+, Ca2+ and N as NO3- in plant nutrient medium in combination or alone brought about a marked stimulation in control plants and moderated the salinity caused reductions in NaCl treated plants. In addition, plants also exhibited differences in these parameters at two growth stages. This revised version was published online in July 2006 with corrections to the Cover Date.     

Modification of foliar solute concentrations by calcium in two species of wheat stressed with sodium chloride and/or potassium chloride

The effects of saline-stresses due to different salts on growth and on foliar solute concentrations in seedlings of two species of wheat that differed in salt tolerance. Triticum aestivum L. cv. Probred and Triticum turgidum L. (Durum group) cv. Aldura, were studied. Triticum aestivum is the more salt tolerant species. The salts used were NaCl, KCI, a 1:1 mixture of NaCI and KCI, and these same monovalent cation salts but mixed with CaCI₂ at a ratio of 2:1 on a molar basis of monovalent to divalent cation salts. Growth inhibition of both species was a function of media osmotic potentials. There was a small additional inhibition of growth if KCI replaced NaCI as the salinizing salt. CaCI₂ had little or no effect on growth inhibition beyond an osmotic effect except at the most severe stress level, i.e. when Ca²⁺ concentrations may be excessive. The amounts of water-soluble Ca²⁺ were about 10 times higher in leaves of plants grown in the presence of CaCI₂ than in its absence, but its concentrations even then were approximately 10% or less of those of the monovalent cations. Including CaCI₂ in growth media resulted in a reduction in the amount of Na⁺ in leaves compared to the amounts in plants grown at the same osmotic potential but in the absence of CaCI₂. Triticum aestivum was a better Na⁺-excluder than T. turgidum. With CaCI₂ in media, (Na⁺+ K⁺) remained relatively constant or increased by small amounts as media osmotic potentials décreased. In the absence of CaCI₂₊ (Na⁺+ K⁺) increased by large amounts when media osmotic potentials were at ?0.6 and ?0.8 MPa. It is concluded that the accumulation system in leaves for monovalent cations was under feed-back control, and that this control mechanism was inhibited by high media concentrations of Na⁺ and/or K⁺. Sucrose was present at a constant amount under all growth conditions. Proline started accumulating when (Na⁺+ K⁺) exceeded a threshold value of 200 μmol (g fresh weight)^?1. Its concentration was 5 to 13% of that portion of (Na⁺+ K⁺) that exceeded the threshold value.     

Effects of potassium carbonate as an alternative road de-icer to sodium chloride on soil chemical properties

The effect of potassium carbonate on soil chemical characteristics was compared with that of the most common de‐icer, sodium chloride, in a 4‐yr outdoor pot experiment with poplar and lime trees. Soil pH was raised more by K₂CO₃ than by NaCl. Potassium carbonate increased the electrical conductivity mainly in the upper soil layers. When K₂CO₃ was applied at an average annual dose of 154 g m^?2, only the water‐soluble fractions of calcium and magnesium were affected. At an average annual dose of 617 g m^?2, total potassium increased by 33% and calcium was displaced from the exchange sites. Calcium saturation was reduced from 85% of the cation exchange capacity in the untreated control to 69% in the higher dose K₂CO₃ treatment and to 75% in the NaCl treatment. The results show that the negative impact of K₂CO₃ on soil chemical and osmotic properties is as high as that of NaCl. For plants, however, potassium carbonate in contrast to chloride is not toxic and, applied in moderate doses, may even remedy potassium deficiencies in roadside trees.     

Free concentrations of sodium, potassium and calcium in chromaffin granules.

We have measured the contents of Na+ and K+ in isolated chromaffin granules. Total contents varied between 227 and 283 nmol/mg of protein, equivalent to matrix concentrations of 53-66 mM. The value found depended on the isolation buffer used, and the ratio of the two ions reflected the composition of the buffer. We then measured the free concentration of each of these ions, and of Ca2+, in the matrix, by using a null-point method with acridine-fluorescence quenching. This monitored H+ fluxes induced by an ionophore in the presence of known concentrations of the ion in the supporting medium. In contrast with organic constituents of the matrix, which have low activity coefficients, Na+ and K+ were found to have activity coefficients around 0.8 Ca2+, however, was strongly bound: its free concentration was only 0.03% of the total.     

Determination of the sodium,potassium and chloride ion concentrations in the chloroplasts of the halophyteSuaeda maritima by non-aqueous cell fractionation

Summary Leaf material from the halophyteSuaeda maritima L. Dum. grown under both saline and non-saline conditions was fractionated under non-aqueous conditions in order to determine the ion content of various subcellular compartments. Fractions containing cell walls, nuclei and chloroplasts were successfully prepared and contents of DNA, chlorophyll, protein and Na⁺, K⁺, and Cl^– determined. The cell wall fraction was not apparently heavily contaminated by the other fractions and had a low ion content although the nuclear fraction was contaminated by other organelles. The ion contents of chloroplasts were determined and the results discussed in relation to earlier microscopical data.     

Sodium,potassium, chloride and proline concentrations of chloroplasts isolated from a halophyte,Mesembryanthemum crystallinum L.

Concentrations of four major solutes (Na⁺, K⁺, Cl^-, proline) were determined in isolated, intact chloroplasts from the halophyte Mesembryanthemum crystallinum L. following long-term exposure of plants to three levels of NaCl salinity in the rooting medium. Chloroplasts were obtained by gentle rupture of leaf protoplasts. There was either no or only small leakage of inorganic ions from the chloroplasts to the medium during three rapidly performed washing steps involving precipitation and re-suspension of chloroplast pellets. Increasing NaCl salinity of the rooting medium resulted in a rise of Na⁺ und Cl^- in the total leaf sap, up to approximately 500 and 400 mM, respectively, for plants grown at 400 mM NaCl. However, chloroplast levels of Na⁺ und Cl^- did not exceed 160–230 and 40–60 mM, respectively, based upon a chloroplast osmotic volume of 20–30 l per mg chlorophyll. At 20 mM NaCl in the rooting medium, the Na⁺/K⁺ ratio of the chloroplasts was about 1; at 400 mM NaCl the ratio was about 5. Growth at 400 mM NaCl led to markedly increased concentrations of proline in the leaf sap (8 mM) compared with the leaf sap of plants grown in culture solution without added NaCl (proline 0.25 mM). Although proline was fivefold more concentrated in the chloroplasts than in the total leaf sap of plants treated with 400 mM NaCl, the overall contribution of proline to the osmotic adjustment of chloroplasts was small. The capacity to limit chloroplast Cl^- concentrations under conditions of high external salinity was in contrast to an apparent affinity of chloroplasts for Cl^- under conditions of low Cl^- availability.Abbreviation Chl chlorophyll     

Effects of sodium chloride stress and calcium supply on growth, potassium uptake, and internal chloride and sodium levels of winter wheat seedlings

The effects of saline conditions on the K+ (86Rb), Na+ and Cl- uptake and growth of 6-day-old wheat (Triticum aestivum L. cv. GK Szeged) seedlings were studied in the absence and presence of Ca2+. It was found that on direct NaCl treatment the K+ uptake of the roots in the absence of Ca2+ declined significantly with increasing salinity. The reverse was true, however, in the case of NaCl pretreatment: seedlings grown under highly saline conditions (50 mM NaCl) absorbed more K+ than those pretreated with low levels of NaCl (1 or 10 mM NaCl). The data indicate a definite Na(+)-induced K+ uptake inhibition and/or feed-back regulation in the K+ uptake of roots under the above-mentioned growth conditions. As regards the Ca2+ effect, it was established that supplemental Ca2+ counteracts the unfavourable effect of saline conditions as concerns both the K+ uptake of the roots and the dry matter yield of the seedlings. The internal concentrations of Na+ and Cl- in the seedlings increased in proportion to increasing salinity. Marked differences were experienced, however, in the internal concentrations of Na+ and Cl- in the roots and shoots, respectively. It was concluded that under these experimental conditions the salt tolerance of wheat could be related to its capability of restricting the transport of Na+ at low and moderate levels to the shoots, where it is highly toxic.