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  • Articles: DFG German National Licenses  (2)
  • 1995-1999  (2)
  • 1975-1979
  • Organic osmolytes  (2)
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  • Articles: DFG German National Licenses  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Cellular response to osmotic stress in the renal medulla (1998)
    Springer
    Pflügers Archiv 436 (1998), S. 814-827 
    Details
    ISSN: 1432-2013
    Keywords: Key words Antidiuresis ; Diuresis ; Heat shock proteins ; Ionic strength ; Organic osmolytes ; Osmotic stress ; Renal medulla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Cells of the renal medulla, which are exposed under normal physiological conditions to widely fluctuating extracellular solute concentrations, respond to hypertonic stress by accumulating the organic osmolytes glycerophosphorylcholine (GPC), betaine, myo-inositol, sorbitol and free amino acids. Increased intracellular contents of these osmolytes are achieved by a combination of increased uptake (myo-inositol and betaine) and synthesis (sorbitol, possibly GPC), decreased degradation (GPC) and reduced osmolyte release. In the medulla of the concentrating kidney, accumulation of organic osmolytes, which do not perturb cell function even at high concentrations, allows the maintenance of ”normal” intracellular concentrations of inorganic electrolytes. Adaptation to decreasing extracellular solute concentrations, e.g. diuresis, is achieved primarily by activation of pathways allowing the efflux of organic osmolytes, and secondarily by inactivation of production (sorbitol) and uptake (betaine, myo-inositol) and stimulation of degradation (GPC). Apart from modulation of the osmolyte content, osmolality-dependent reorganization of the cytoskeleton and expression of specific stress proteins (heat shock proteins) may be further, as yet poorly characterized, components of the regulatory systems involved in the adaptation of medullary cells to osmotic stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050710
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Pretreatment with hypertonic NaCl protects MDCK cells against high urea concentrations (1998)
    Springer
    Pflügers Archiv 435 (1998), S. 407-414 
    Details
    ISSN: 1432-2013
    Keywords: Key words MDCK cells ; Hypertonic stress ; NaCl ; Urea ; Organic osmolytes ; Heat shock proteins ; Cell viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  In antidiuresis, the cells of the renal medulla are exposed to high extracellular concentrations of NaCl and urea. Since urea equilibrates with the intracellular compartment and is known to perturb intracellular macromolecules, high urea concentrations may well disturb the structure and function of cell proteins. Two types of organic substances are believed to counteract the adverse effects of high intracellular urea concentrations: specific organic osmolytes of the trimethylamine family [betaine and glycerophosphorylcholine (GPC)], which accumulate in renal medullary cells during prolonged periods of antidiuresis and cytoprotective heat shock proteins (HSPs), the tissue content of two of which (HSPs 27 and 72) is much higher in the inner medulla than in the iso-osmotic renal cortex. To evaluate the contribution of trimethylamines and HSPs to cytoprotection in the presence of high urea concentrations, the effect of HSP induction and osmolyte accumulation prior to exposure to high urea concentrations was examined in Madin-Darby canine kidney (MDCK) cells. Accumulation of organic osmolytes and synthesis of HSP27 and HSP72 was initiated by hypertonic stress (increasing the osmolality of the medium from 290 to 600 mosmol/kg H2O by NaCl addition). Control, non-conditioned cells remained in the isotonic medium for the same period. Upon subsequent exposure to an additional 600 mM urea in the medium for 24 h, 90% of the osmotically conditioned cells but only 15% of non-conditioned cells survived. The HSP72 and trimethylamine contents of the NaCl-conditioned MDCK cells, but not HSP27 content, correlated positively with cell survival. To separate the effects of organic osmolytes and HSP72, chronically NaCl-adapted MDCK cells were returned to isotonic medium for 1 or 2 days, so depleting them of trimethylamine osmolytes. HSP72, with its longer half life, remained elevated. Subsequent exposure of these cells to 600 mM urea in the medium resulted in about 80% survival. These results suggest that in MDCK cells and probably in the renal medulla, HSP72 and perhaps additional protective factors contribute substantially to the resistance against high urea concentrations.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004240050531
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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