title: Osmoregulation of aldose reductase and sorbitol dehydrogenase in cultivated interstitial cells of rat renal inner medulla.
abstract: BACKGROUND
  Little is known about sorbitol metabolism in renal papillary interstitial cells. For characterization we studied regulation of sorbitol synthesis by aldose reductase (AR) and degradation by sorbitol dehydrogenase (SDH) in papillary interstitial cells.
  
  
  METHODS
  Interstitial cells were isolated from rat renal inner medulla to a pure cell fraction. mRNA was isolated from cultivated cells and sorbitol, AR and SDH activity were determined enzymatically in homogenates.
  
  
  RESULTS
  Sorbitol concentration in these cells at 300 mosmol/l was 4.4+/-0.3 vs 78+/-3.6 micro mol/g protein at 600 mosmol/l. At steady-state conditions at 300 mosmol/l, AR activity was nearly the same as SDH activity (15.1+/-1.6 vs 16.6+/-2.0 U/g protein). At 600 mosmol/l, AR activity increased to 82.5+/-11.4 U/g protein and SDH activity to 31.5+/-6.0 U/g protein. Studying the time course of enzyme activity after changing osmolarity from 300 to 600 mosmol/l, we found half maximal stimulation after 2-3 (AR) or 3 (SDH) days. The amount of AR-mRNA preceded the rise of enzyme activity, whereas SDH-mRNA was not significantly influenced. Lowering osmolarity from 600 to 300 mosmol/l, enzyme activity decreased to less than half within 2 (AR) or 1 (SDH) day(s).
  
  
  CONCLUSIONS
  The results suggest that sorbitol metabolism contributes to handling of osmotic stress in rat renal papillary interstitial cells.
authors.affiliation: Abteilung Nephrologie und Rheumatologie, Georg-August-Universität Göttingen, Göttingen, Germany. jsteffgen@gmx.de
authors.forename: Jürgen
authors.initials: J
authors.lastname: Steffgen
authors.forename: Katrin
authors.initials: K
authors.lastname: Kampfer
authors.forename: Clemens
authors.initials: C
authors.lastname: Grupp
authors.forename: Christoph
authors.initials: C
authors.lastname: Langenberg
authors.forename: Gerhard A
authors.initials: GA
authors.lastname: Müller
authors.forename: R Willi
authors.initials: RW
authors.lastname: Grunewald
mesh_terms: D000449:Aldehyde Reductase / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018929:Cell Culture Techniques; D005347:Fibroblasts / Q000201:enzymology; D007679:Kidney Medulla / Q000201:enzymology*; D007685:Kidney Tubules, Collecting / Q000201:enzymology*; D007064:L-Iditol 2-Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D013012:Sorbitol / Q000378:metabolism; D014882:Water-Electrolyte Balance / Q000502:physiology*
chemical_list: D012333:RNA, Messenger; D013012:Sorbitol; D007064:L-Iditol 2-Dehydrogenase; D000449:Aldehyde Reductase