title: pH-dependent regulation of leukocyte 5-lipoxygenase activity in inflammatory exudates by albumin.
abstract: OBJECTIVE
  In order to study the regulation of cellular 5-lipoxygenase activity under inflammatory conditions, the effects of inflammatory exudates on rat leukocyte 5 lipoxygenase activity were investigated.
  
  
  METHODS
  Peritoneal leukocytes and inflammatory exudates were collected from glycogen treated rats.
  
  
  METHODS
  Glycogen (1 g/kg body weight, in a final volume of 3 ml PBS) was injected intraperitoneally into male Wistar rats. After 4 h, the inflammatory exudate was collected.
  
  
  METHODS
  Rat peritoneal leukocytes were isolated and the cellular 5-lipoxygenase activity was determined by HPLC after cell stimulation with calcium ionophore A23187.
  
  
  RESULTS
  Inflammatory exudates from glycogen treated animals strongly inhibited cellular 5-lipoxygenase activity of ionophore challenged leukocytes. Albumin was identified as the inhibitor in exudates. Inhibition of cellular 5-lipoxygenase activity by albumin was pH-dependent and was strongly increased by the alkaline pH (7.9-8.0) of the exudate. The albumin effect increased in the range of pH 7.4-8.2 where albumin undergoes a conformational change called neutral to base (N-B) transition. S-Carboxymethyl-albumin had a similar activity to that of albumin, which indicated that the free SH-group at Cys-34 of albumin is not necessary for the effect. The albumin dimer showed a significantly higher inhibition than albumin and it suppressed cellular 5-lipoxygenase activity by 98%. Peptic and tryptic fragments of albumin which comprise domains I, II and II, III, respectively, were less active or inactive. Thus, an intact albumin molecule or the dimer are required for efficient inhibition of cellular 5-lipoxygenase activity.
  
  
  CONCLUSIONS
  Our data suggest that during inflammation, albumin extravasation and changes in pH-value are involved in the regulation of the inflammatory reaction by suppression of leukotriene release.
authors.affiliation: Institute of Pharmaceutical Chemistry, University of Frankfurt, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Benz
authors.forename: O
authors.initials: O
authors.lastname: Werz
authors.forename: R
authors.initials: R
authors.lastname: Jacob
authors.forename: D
authors.initials: D
authors.lastname: Steinhilber
mesh_terms: D000818:Animals; D001094:Arachidonate 5-Lipoxygenase / Q000378:metabolism*; D001202:Ascitic Fluid / Q000201:enzymology*; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006003:Glycogen; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007962:Leukocytes / Q000201:enzymology*; D016859:Lipoxygenase Inhibitors; D008297:Male; D010446:Peptide Fragments / Q000494:pharmacology; D010533:Peritoneal Lavage; D010538:Peritonitis / Q000139:chemically induced / Q000201:enzymology*; D051381:Rats; D017208:Rats, Wistar; D012709:Serum Albumin / Q000494:pharmacology*; D012710:Serum Albumin, Bovine / Q000494:pharmacology
chemical_list: D004791:Enzyme Inhibitors; D016859:Lipoxygenase Inhibitors; D010446:Peptide Fragments; D012709:Serum Albumin; D012710:Serum Albumin, Bovine; D006003:Glycogen; D001094:Arachidonate 5-Lipoxygenase