title: Dose-dependent protective effect of L-carnitine on oxidative stress in the livers of hyperthyroid rats.
abstract: OBJECTIVE
  The present study was designed to investigate the dose-dependent protective effect of L-carnitine (LC) on thyroid hormone-induced oxidative stress in rat liver tissue.
  
  
  METHODS
  Twenty-one male Sprague Dawley rats were divided into four groups: control, hyperthyroidism, hyperthyroidism plus L-carnitine 100, and hyperthyroidism plus L-carnitine 500. Hyperthyroidism was induced in rats by injecting 250 μg of L-thyroxine/kg body weight/day for twenty consecutive days. The activities of catalase (CAT), glutathione peroxidase (GPX) and myeloperoxidase (MPO) and the level of malondialdehyde (MDA) were measured in liver homogenates.
  
  
  RESULTS
  The liver CAT, GPX and MPO activities were significantly lower in the hyperthyroid rats than in the control group. Treating hyperthyroid rats with both low-dose (100 mg/kg) and high-dose (500 mg/kg) L-carnitine for 10 days resulted in a marked increase in the activities of the antioxidant enzymes in the liver tissue.
  
  
  CONCLUSIONS
  The present study indicates that the low-dose L-carnitine application was sufficient to prevent L-thyroxine-induced oxidative stress in rat livers.
authors.affiliation: Department of Physiology, Faculty of Medicine, Ataturk University, Erzurum, Turkey.
authors.forename: Serap
authors.initials: S
authors.lastname: Yildirim
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Ataturk University, Erzurum, Turkey.
authors.forename: Abdulkadir
authors.initials: A
authors.lastname: Yildirim
authors.affiliation: Department of Physiology, Faculty of Medicine, Fatih University, Ankara, Turkey.
authors.forename: Senol
authors.initials: S
authors.lastname: Dane
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Ataturk University, Erzurum, Turkey.
authors.forename: Elvin
authors.initials: E
authors.lastname: Aliyev
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Fatih University, Ankara, Turkey.
authors.forename: Ramazan
authors.initials: R
authors.lastname: Yigitoglu
keywords: Catalase; L-carnitine; Liver; Malondialdehyde; Myeloperoxidase; glutathione peroxidase