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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Journal of molecular medicine 66 (1988), S. 843-848 
    ISSN: 1432-1440
    Keywords: Renal papillary cells ; Cell electrolytes ; Osmoadaptation ; Organic osmolytes ; Electron microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The cells of the renal papilla are subject to extreme variations in extracellular tonicity. To obtain more insight into the mechanisms whereby these cells adapt osmotically to these unique environmental conditions, elements were measured in individual cells of the rat renal papilla in antidiuresis and after prolonged furosemide administration. In antidiuresis cell sodium, chloride and potassium concentrations did not differ fundamentally from those observed in tubule cells exposed to isotonic surroundings such as in proximal tubule cells. The marked fall in extracellular electrolyte concentrations induced by furosemide was paralleled by a far less pronounced decline in intracellular sodium, chloride and potassium concentrations. These data indicate that papillary cells achieve osmoadaptation to widely differing extracellular tonicities mainly by varying the intracellular concentrations of osmotically active substances other than inorganic electrolytes. Since high concentrations of organic osmolytes (sorbitol, inositol, glycerophosphorylcholine and other trimethylamines) have been detected in the papilla and since the tissue contents of these compounds have been shown to vary in parallel with urine osmolality, it may be concluded that metabolically inert, organic osmolytes play a dominant role in the osmoregulation of renal papillary cells.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1440
    Keywords: Electron microprobe analysis ; Intracellular electrolytes ; Kidney ; Ischaemia ; Elektronenstrahl-Mikroanalyse ; Intrazelluläre Elektrolyte ; Niere ; Ischämie
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In order to be able to examine the processes involved in transepithelial transport in tissues, which are not composed of a single cell type, methods are required, which permit analysis at a cellular level. The technique of electron microprobe analysis permits the intracellular concentrations of many elements to be determined simultaneously in various portions of the cell. The application of this method to renal cortical tissue has shown that the best estimates of the cytoplasmic concentrations are to be obtained in regions close to the nucleus, farthest from the basolateral infoldings and microvilli, which separate the intracellular environment from the extracellular space. The nuclear concentrations of Na and K do not differ from those in the surrounding cytoplasm, although those of P and C1 are somewhat higher in cytoplasm. The intracellular element concentrations in the different cell types vary somewhat, proximal tubular cells contain higher concentrations of Na and C1 and lower ones of P than distal tubular cells. Following ischaemia, a manoeuvre know to result in a disturbance of intracellular electrolytes, Na was observed to rise and K to fall only in the non-surface cells of kidneys exposed to the air, but in all cells, if the kidneys were kept air-free in an atmosphere of N2. The proximal and distal tubular cells showed a variable resistance to ischaemia, the distal tubular cells being much more resistant. Despite the severity of the electrolyte disturbance following ischaemia, the intracellular composition was completely restored one hour after re-introducing renal blood flow.
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  • 3
    ISSN: 1432-2013
    Keywords: Electron microprobe analysis ; Volume expansion ; Intracellular electrolytes ; Renal tubular cells ; Natriuretic mechanisms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract It has previously been shown that during mannitol-saline volume expansion (VE) Na transport was inhibited 50% by harvested proximal tubular fluid without a change in paracellular shunt pathway permeability to Na. To determine whether this inhibition was due to changes in cellular entry step or an effect on the pump itself, intracellular element concentrations were measured by electron microprobe X-ray ranalysis in proximal tubular cells of control (non-expanded, NE) and VE rats. Na i , Cl i and phosphorus i were increased (mean±S.E.) from 19.3±0.8 to 23.4±0.6, 15.8±0.4 to 21.3±0.4 and 124.3±2.6 to 138.0±1.8 mmol · kg−1 wet weight (P〈0.001) respectively while K i remained unchanged: 122.9±2.2 and 124.2±1.3 mmol · kg−1 wet weight. The increases in Na i and Cl i were in excess of cell shrinkage produced by the hyperosmolal peritubular environment while the unchanged K i in the face of cell shrinkage indicates and actual loss. It is concluded that mannitol-saline VE inhibits the Na pump producing a rise in Na i and a fall in K i .
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  • 4
    ISSN: 1432-2013
    Keywords: Key words Unidirectional Rb fluxes ; Electron microprobe analysis ; Luminal Rb uptake ; Cellular element concentrations ; Ouabain ; Ethoxzolamide ; Amiloride
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The mammalian distal colon, which is composed of different cell types, actively transports Na, K and Cl in absorptive and K and Cl in secretory directions. To further characterize the K absorption process and to identify the cells involved in K absorption, unidirectional Rb fluxes and luminal Rb uptake into different epithelial cell types were determined in isolated guinea-pig distal colon. Net Rb absorption (1.5–2.5 µmol·h–1·cm–2) was not influenced by inhibition of Na transport with amiloride or by incubating both sides of the epithelium with Na-free solutions, but was almost completely abolished by luminal ouabain, ethoxzolamide or by incubating both sides of the epithelium with Cl-free solutions. Luminal Rb uptake, blockable by luminal ouabain, preferentially occurred in columnar surface and neck cells, to a lesser extent in surface goblet cells and to an insignificant degree in lower crypt cells. Employing a luminal Rb-Ringer (5.4 mM Rb) the Rb concentration increased within 10 min in columnar surface and neck, surface goblet and lower crypt cells to 70, 32 and about 10 mmol·kg–1 wet weight, respectively. The presence of 5.4 mM K in the luminal incubation solution reduced Rb uptake almost completely indicating a much higher acceptance of the luminal H-K-ATPase for K than for Rb. The increase in Na and decrease in K concentrations in surface and neck cells induced by luminal ouabain might indicate inhibition of the basolateral Na-K-ATPase or drastic enhancement of cellular Na uptake by the Na-H exchanger. Bilateral Na-free incubation did not alter Rb uptake, but bilateral Cl-free incubation drastically reduced it. Inhibition of net Rb absorption by ethoxzolamide and inhibition of both Rb absorption and Rb uptake by bilateral Cl-free incubation support the notion that cellular CO2 hydration is a necessary prerequisite for K absorption and that HCO3 leaves the cell via a Cl-HCO3 exchanger. Since ouabain-inhibitable transepithelial Rb flux and luminal Rb uptake rate by surface and neck cells were about the same, Rb(K) absorption seems to be accomplished mainly by columnar surface cells.
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  • 5
    ISSN: 1432-2013
    Keywords: Electron microprobe analysis ; Sympathetic neurones ; Cellular electrolyte concentrations ; Carbachol ; Ouabain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Intracellular element concentrations were measured in rat sympathetic neurones using energy dispersive electron microprobe analysis. The resting intracellular concentrations of sodium potassium and chloride measured in ganglia maintained for about 90 min in vitro at 25° C were 3, 155 and 25 mmol/kg total tissue wet weight respectively. Recalculated in mmol/l cell water, these values are 5, 196 and 32 respectively. There were no significant differences between the nuclear and cytoplasmic values of these ions. Incubation in either carbachol (108 μmol/l, 4 min) or ouabain (1 mmol/l, 60 min) significantly increased the intracellular sodium and decreased the intracellular potassium concentrations. Neither substance materially altered the intracellular chloride concentration. The data obtained are compared and contrasted to those obtained in mammalian sympathetic neurones using chemical analysis and ion-sensitive microelectrodes.
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  • 6
    ISSN: 1432-2013
    Keywords: Acute metabolic acidosis ; Renal distal electrolyte transport ; Renal cell electrolyte concentrations ; Individual distal tubule cells ; Transmembrane electrolyte concentration gradients ; Electron microprobe analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We studied the effect of acute metabolic acidosis on potassium, sodium and chloride gradients across the apical membrane of proximal and distal tubule cells by determining electrolyte concentrations in individual cells and in tubule fluid employing electron microprobe analysis. Cellular measurements were performed on freeze-dried cryosections of the renal cortex, analysis of tubule fluid electrolyte concentrations on freeze-dried microdroplets of micropuncture samples obtained from proximal and from early and late distal collection sites. Acidosis (NH4Cl i.v. and i.g.) induced a substantial rise in plasma potassium concentration without significant effects on cell potassium concentrations. Potassium concentrations along the surface distal tubule were also unaltered; thus the chemical driving force for potassium exit from cell to lumen was not affected by acidosis. In all but intercalated cells acidosis markedly increased cell phosphorus concentration and cell dry weight indicating cell shrinkage and thus diminution of cell potassium content. Because the increase in intracellular chloride concentration exceeded the increase in plasma chloride concentration, the chemical chloride gradient across the contraluminal membrane was markedly depressed by acidosis.
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  • 7
    ISSN: 1432-2013
    Keywords: Single renal tubules ; Electron microprobe analysis ; Cellular concentrations
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract A method is described whereby single renal tubules, incubated in varying incubation media can be captured and prepared for electron microprobe analysis for intracellular sodium, potassium, chloride, phosphorus, magnesium amongst others.
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