title: Methylprednisolone inhibits low-flow hypoxia-induced mitochondrial dysfunction in isolated perfused rat liver.
abstract: OBJECTIVE
  To investigate the mechanism by which methylprednisolone protects the liver from hypoxia-induced injury.
  
  
  METHODS
  Prospective control study using the isolated rat liver.
  
  
  METHODS
  Animal research facility.
  
  
  METHODS
  Male, fasted, pathogen-free Sprague-Dawley rats.
  
  
  METHODS
  Low-flow hypoxia was produced by reducing afferent perfusate pressure from 10 to 2.5 cm H(2)O; isolated livers were portally perfused for 2 hrs.
  
  
  RESULTS
  We measured mitochondrial membrane potential and hydrogen peroxide production by imaging rhodamine 123 and 2'-7'-dichlorofluorescein fluorescence, respectively. Leakage of mitochondrial enzymes was also monitored by assaying mitochondrial aspartate aminotransferase activity in the outflow perfusate, and the radical-scavenging effect of methylprednisolone was assessed by measuring luminol-dependent hydrogen peroxide chemiluminescence. Apoptosis in liver cells was determined by using terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick-end labeling. Rhodamine 123 fluorescence was significantly diminished in the hypoxic liver, especially in the region of the terminal hepatic venules, which is indicative of membrane depolarization in the mitochondria in those areas. Hypoxia-induced mitochondrial dysfunction was indicated by leakage of aspartate aminotransferase into the outflow perfusate, and increased 2'-7'-dichlorofluorescein fluorescence indicated increased hydrogen peroxide levels, particularly in the midzone. Pretreatment with 30, 10, or 3 mg/kg of methylprednisolone inhibited the hypoxia-induced mitochondrial membrane depolarization and enzyme leakage, although hydrogen peroxide levels and apoptosis in sinusoidal endothelial cells were unaffected.
  
  
  CONCLUSIONS
  Methylprednisolone does not protect the liver from hypoxia-induced injury by suppressing hydrogen peroxide production. Instead, the beneficial effect of methylprednisolone seems to be related to its ability to protect against mitochondrial membrane depolarization under hypoxic conditions.
authors.affiliation: Second Department of Surgery, Akita University School of Medicine, Akita City, Japan.
authors.forename: Satoru
authors.initials: S
authors.lastname: Motoyama
authors.forename: Satoshi
authors.initials: S
authors.lastname: Saito
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Minamiya
authors.forename: Reijiro
authors.initials: R
authors.lastname: Saito
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Nakamura
authors.forename: Manabu
authors.initials: M
authors.lastname: Okuyama
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Imano
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Ogawa
mesh_terms: D000818:Animals; D000893:Anti-Inflammatory Agents / Q000494:pharmacology / Q000627:therapeutic use*; D017209:Apoptosis; D024442:Aspartate Aminotransferase, Mitochondrial / Q000032:analysis; D004195:Disease Models, Animal; D004353:Drug Evaluation, Preclinical; D016166:Free Radical Scavengers / Q000494:pharmacology / Q000627:therapeutic use; D006861:Hydrogen Peroxide / Q000032:analysis; D000860:Hypoxia / Q000201:enzymology / Q000209:etiology / Q000517:prevention & control*; D020287:In Situ Nick-End Labeling; D066298:In Vitro Techniques; D008099:Liver / Q000098:blood supply*; D008163:Luminescent Measurements; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D008775:Methylprednisolone / Q000494:pharmacology / Q000627:therapeutic use*; D008930:Mitochondria, Liver; D028361:Mitochondrial Diseases / Q000201:enzymology / Q000209:etiology / Q000517:prevention & control*; D011446:Prospective Studies; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D000893:Anti-Inflammatory Agents; D016166:Free Radical Scavengers; D006861:Hydrogen Peroxide; D024442:Aspartate Aminotransferase, Mitochondrial; D008775:Methylprednisolone