title: In vitro effect of melatonin on oxygen consumption in liver mitochondria of rats.
abstract: OBJECTIVE
  To examine the in vitro effect of melatonin on rat mitochondrial liver respiration.
  
  
  METHODS
  Oxygen consumption by liver mitochondria was measured polarographically in the presence of one of the following Krebs' cycle substrates: Lsuccinate, DL-3- beta-hydroxybutyrate or L-malate. Respiratory velocities at rest (state 4) and during rapid respiration in the presence of substrate and adenosine diphosphate (state 3) were measured in the presence of 10 (-9)-10(-3) M concentrations of melatonin.
  
  
  RESULTS
  In vitro melatonin (10(-7)-10(-3) M) reduced state 3 mitochondrial respiration. Basal, state 4 respiration was not affected by melatonin. Consequently, control respiratory index (i.e., the ratio of state 3 to state 4 respiration) was inhibited by melatonin with a threshold at 10(-7) M concentration.
  
  
  CONCLUSIONS
  The ability of melatonin to curtail acutely the stimulation of oxygen consumption in liver mitochondria may protect the mitochondria from excessive oxidative damage.
authors.affiliation: Departamento de Fisiologia and Hospital de Clinicas, Facultad de Medicina, Universidad de Buenos Aires, Buenos Aires, Argentina.
authors.forename: Carlos F
authors.initials: CF
authors.lastname: Reyes-Toso
authors.forename: Conrado R
authors.initials: CR
authors.lastname: Ricci
authors.forename: Inés R
authors.initials: IR
authors.lastname: de Mignone
authors.forename: Patricia
authors.initials: P
authors.lastname: Reyes
authors.forename: Laura M
authors.initials: LM
authors.lastname: Linares
authors.forename: Liliana E
authors.initials: LE
authors.lastname: Albornoz
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Cardinali
authors.forename: Angel
authors.initials: A
authors.lastname: Zaninovich
mesh_terms: D020155:3-Hydroxybutyric Acid / Q000378:metabolism; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D066298:In Vitro Techniques; D008293:Malates / Q000378:metabolism; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D010101:Oxygen Consumption / Q000187:drug effects*; D051381:Rats; D017208:Rats, Wistar; D019802:Succinic Acid / Q000378:metabolism
chemical_list: D000975:Antioxidants; D008293:Malates; C030298:malic acid; D019802:Succinic Acid; D008550:Melatonin; D020155:3-Hydroxybutyric Acid