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  • 1
    ISSN: 1432-2013
    Keywords: Key words Diuresis/antidiuresis ; Osmotic stress ; HSP25 ; HSP60 ; HSP72 ; HSP73 ; Transcription ; Translation ; Medullary hypertonicity ; Phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The influence of diuresis and antidiuresis on the expression of heat shock proteins (HSP) 25, 60, 72 and 73 in the renal cortex and outer and inner medulla of Wistar rats was analysed. Medullary osmolality was reduced by long-term diuresis (3% sucrose in the drinking water for 3 weeks) and subsequently enhanced by transition to a concentrating state by giving normal drinking water again in combination with deamino-D-arginine vasopressin (dDAVP) for 5 days. Western blot analyses revealed that neither HSP73 nor HSP60 was influenced by any treatment. The HSP72 level in the medulla was markedly reduced (50%) when osmolality was lowered and increased when tonicity was high. RNAse protection assays showed that the effects on HSP72 are parallelled in general by changes in HSP72 mRNA. While levels of HSP25 were not influenced, isoelectric focusing revealed that the degree of phosphorylation of outer and inner medullary HSP25 increased following both treatments. It thus seems that HSP73 and HSP60 are not directly involved in the long-term adaptation to varying medullary osmolalities. The correlation between changes in osmolality and amounts of the major stress-inducible HSP72 in the medulla implies that medullary hypertonicity is stressful for kidney cells. Furthermore, adaptation to pronounced changes in the osmolality of the environment most likely involves phosphorylation of HSP25.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 434 (1997), S. 117-122 
    ISSN: 1432-2013
    Keywords: Key words Organic osmolytes ; Urea ; Intracellular electrolytes ; Heat shock proteins ; HSP25 ; HSP72 ; Osmoregulation ; Kidney
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  The high content of heat shock proteins (HSPs) 25 and 72 in the hyperosmotic inner medulla of the concentrating kidney has been ascribed to the high NaCl and urea concentrations in this kidney zone. To assess the effects of variations in the composition of solutes in the renal medulla on the intrarenal distribution of HSPs, rats were fed either a high- or low-Na diet for 3 weeks. These diets result in greatly differing urine and inner medullary solute composition. Sodium dodecyl sulphate polyacrylamide gel electrophoresis and Western blot techniques were used to analyse HSP25 and HSP72 in the cortex, outer medulla and inner medulla. In addition, the amounts of organic osmolytes (sorbitol, myo-inositol, betaine and glycerophosphorylcholine) and urea in the tissue were determined by high-performance liquid chromatography. Intra- and extracellular electrolyte concentrations at the papillary tip were measured by electron microprobe analysis. In the high-Na group, urine osmolality was about 1000 mosmol/kg lower than in rats fed a low-Na diet, due to lower urea concentrations. The sum of urine sodium and potassium concentrations, however, did not differ between the two groups. Neither in the outer nor in the inner medulla was the sum of the concentrations of organic osmolytes affected by the dietary treatment. The sum of sodium, potassium and chloride concentrations did not differ between the two experimental groups, neither in the interstitial nor in the intracellular compartments. However, the urea content and the amounts of HSP25 and HSP72 were significantly lower in the inner medulla of the group of rats fed a high-Na diet. Our results suggest that urea participates in the regulation of the medullary levels of the HSPs and that both HSP25 and HSP72 are components of mechanisms protecting medullary cells against the deleterious effects of high urea concentrations.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Pflügers Archiv 434 (1997), S. 292-299 
    ISSN: 1432-2013
    Keywords: Key words Renal ischaemia ; Acute renal failure ; Heat shock proteins ; HSP25 ; HSP72 ; Renal cortex ; Renal outer medulla ; Renal inner medulla
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract  Induction of heat shock proteins (HSPs) following cell injury contributes to the protection of vital cell functions. It was, therefore, of interest to study the effects of transient renal ischaemia on the abundance and distribution of two HSPs, HSP25 and HSP72, in renal tissue using Western-blot techniques. Analyses were performed on the supernatant (HSP25, HSP72) and pellet (HSP25) of homogenates obtained from cortex (CX) and outer (OM) and inner (IM) medulla of the rat kidney immediately after 60 min of ischaemia followed by varying periods of reperfusion. Ischaemia of the left kidney caused HSP25 contents to decrease in CX, OM and IM by 73, 89 and 54% respectively, compared with the corresponding zones of the contralateral control kidney. This initial decrease in supernatant HSP25 was accompanied by an increased abundance of HSP25 in the pellet. Following reperfusion, HSP25 contents in the supernatant gradually increased in CX and OM, reaching, after 24 h, values that were 5.4- and 2.5-fold higher, respectively, than those in the control kidneys. After 7 or 14 days of reperfusion, HSP25 contents had not completely normalised in CX, but had reached control levels in OM. In IM, the HSP25 content remained below control throughout the entire reperfusion period. HSP72 (supernatant) was below the detection limit in the CX of the control kidney. Similar to the level of HSP25, that of HSP72 was also markedly lower in OM and IM immediately after ischaemia. The intrarenal distribution of HSP72 and the sequence of zonal changes in HSP72 contents were similar to those observed for HSP25. These results are compatible with the view that, during ischaemia and the initial reperfusion period, HSP25 migrates from the cytoplasmic compartment (supernatant) into the nucleus and/or associates with cytoskeletal structures. The observation that both HSP25 and HSP72 are transiently induced in CX and OM, but not in IM, may be explained by the fact that, while all kidney cells are exposed to ischaemic stress, only inner medullary cells experience a major postischaemic attenuation of osmotic stress.
    Type of Medium: Electronic Resource
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