title: Hypothyroidism attenuates protein tyrosine nitration, oxidative stress and renal damage induced by ischemia and reperfusion: effect unrelated to antioxidant enzymes activities.
abstract: BACKGROUND
  It has been established that hypothyroidism protects rats against renal ischemia and reperfusion (IR) oxidative damage. However, it is not clear if hypothyroidism is able to prevent protein tyrosine nitration, an index of nitrosative stress, induced by IR or if antioxidant enzymes have involved in this protective effect. In this work it was explored if hypothyroidism is able to prevent the increase in nitrosative and oxidative stress induced by IR. In addition the activity of the antioxidant enzymes catalase, glutathione peroxidase, and superoxide dismutase was studied. Control and thyroidectomized (HTX) rats were studied 24 h of reperfusion after 60 min ischemia.
  
  
  METHODS
  Male Wistar rats weighing 380 +/- 22 g were subjected to surgical thyroidectomy. Rats were studied 15 days after surgery. Euthyroid sham-operated rats were used as controls (CT). Both groups of rats underwent a right kidney nephrectomy and suffered a 60 min left renal ischemia with 24 h of reperfusion. Rats were divided in four groups: CT, HTX, IR and HTX+IR. Rats were sacrificed and samples of plasma and kidney were obtained. Blood urea nitrogen (BUN) and creatinine were measured in blood plasma. Kidney damage was evaluated by histological analysis. Oxidative stress was measured by immunohistochemical localization of protein carbonyls and 4-hydroxy-2-nonenal modified proteins. The protein carbonyl content was measured using antibodies against dinitrophenol (DNP)-modified proteins. Nitrosative stress was measured by immunohistochemical analysis of 3-nitrotyrosine modified proteins. The activity of the antioxidant enzymes catalase, glutathione peroxidase, and superoxide dismutase was measured by spectrophotometric methods. Multiple comparisons were performed with ANOVA followed by Bonferroni t test.
  
  
  RESULTS
  The histological damage and the rise in plasma creatinine and BUN induced by IR were significantly lower in HTX+IR group. The increase in protein carbonyls and in 3-nitrotyrosine and 4-hydroxy-2-nonenal modified proteins was prevented in HTX+IR group. IR-induced decrease in renal antioxidant enzymes was essentially not prevented by HTX in HTX+IR group.
  
  
  CONCLUSIONS
  Hypothyroidism was able to prevent not only oxidative but also nitrosative stress induced by IR. In addition, the antioxidant enzymes catalase, glutathione peroxidase, and superoxide dismutase seem not to play a protective role in this experimental model.
authors.affiliation: Facultad de Química, Departamento de Biología, Universidad Nacional Autónoma de México, Ciudad Universitaria, 04510, México, D.F., Mexico. moni_teve@yahoo.com.mx
authors.forename: Verónica M
authors.initials: VM
authors.lastname: Tenorio-Velázquez
authors.forename: Diana
authors.initials: D
authors.lastname: Barrera
authors.forename: Martha
authors.initials: M
authors.lastname: Franco
authors.forename: Edilia
authors.initials: E
authors.lastname: Tapia
authors.forename: Rogelio
authors.initials: R
authors.lastname: Hernández-Pando
authors.forename: Omar Noel
authors.initials: ON
authors.lastname: Medina-Campos
authors.forename: José
authors.initials: J
authors.lastname: Pedraza-Chaverri
mesh_terms: D000818:Animals; D002374:Catalase / Q000378:metabolism; D005979:Glutathione Peroxidase / Q000378:metabolism; D007037:Hypothyroidism / Q000150:complications*; D007150:Immunohistochemistry; D007668:Kidney / Q000098:blood supply* / Q000378:metabolism / Q000473:pathology*; D008297:Male; D018384:Oxidative Stress; D010088:Oxidoreductases / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000150:complications / Q000378:metabolism / Q000473:pathology*; D013482:Superoxide Dismutase / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
chemical_list: C002744:3-nitrotyrosine; D014443:Tyrosine; D010088:Oxidoreductases; D002374:Catalase; D005979:Glutathione Peroxidase; D013482:Superoxide Dismutase