title: The thyroid hormone receptor β-selective agonist GC-1 does not affect tolerance to exercise in hypothyroid rats.
abstract: OBJECTIVE
  Investigate the effect of GC-1 on tolerance to exercise in rats with experimental hypothyroidism.
  
  
  METHODS
  Hypothyroidism was induced with methimazole sodium and perchlorate treatment. Six groups with eight animals were studied: control group (C), hypothyroid group without treatment (HYPO); hypothyroidism treated with physiological doses of tetraiodothyronine (T4) or 10 times higher (10×T4); hypothyroidism treated with equal molar doses of GC-1 (GC-1) or 10 times higher (10×GC-1). After eight weeks, each animal underwent an exercise tolerance test by measuring the time (seconds), in which the rats were swimming with a load attached to their tails without being submerging for more than 10 sec. After the test, the animals were killed, and blood samples were collected for biochemical analysis, and the heart and soleus muscle were removed for weighing and morphometric analysis of the cardiomyocyte.
  
  
  RESULTS
  Hypothyroidism significantly reduced tolerance to exercise and, treatment with GC-1 1× or T4 in physiological doses recover tolerance test to normal parameters. However, high doses of T4 also decreased tolerance to physical exercise. Conversely, ten times higher doses of GC-1 did not impair tolerance to exercise. Interestingly, hypothyroidism, treated or not with T4 in a physiological range, GC-1 or even high doses of GC-1 (10X) did not change cardiomyocyte diameters and relative weight of the soleus muscle. In contrast, higher doses of T4 significantly increased cardiomyocyte diameter and induced atrophy of the soleus muscle.
  
  
  CONCLUSIONS
  Unlike T4, GC-1 in high doses did not modify tolerance to physical exercise in the rats with hypothyroidism.
authors.affiliation: Faculty of Health Sciences, University of Brasilia, Brasilia, DF, Brazil.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Gonçalves
authors.affiliation: Institute of Health Sciences, University Centre of Planalto de Araxa, Araxa, MG, Brazil.
authors.forename: Chineyder Corrêa
authors.initials: CC
authors.lastname: Tolentino
authors.affiliation: Faculty of Medicine, Federal University of Uberlandia, Uberlandia, MG, Brazil.
authors.forename: Fernanda Rodrigues de
authors.initials: FR
authors.lastname: Souza
authors.affiliation: Institute of Genetics and Biochemistry, UFU, Uberlandia, MG, Brazil.
authors.forename: Juliana Carla da Costa
authors.initials: JC
authors.lastname: Huss
authors.affiliation: Institute of Health Sciences, Central University of Planalto de Araxa, Araxa, MG, Brazil.
authors.forename: Karolinne de Lourdes
authors.initials: Kde L
authors.lastname: Zinato
authors.affiliation: Faculty of Medicine, Federal University of Uberlandia, Uberlandia, MG, Brazil.
authors.forename: Leandro Teixeira Paranhos
authors.initials: LT
authors.lastname: Lopes
authors.affiliation: Faculty of Physical Education, Federal University of Triangulo Mineiro, Uberaba, MG, Brazil.
authors.forename: Roberto
authors.initials: R
authors.lastname: Furlanetto Júnior
authors.affiliation: Molecular Pharmacology Laboratory, Faculty of Health Sciences, UnB, Brasilia, DF, Brazil.
authors.forename: Francisco de Assis Rocha
authors.initials: Fde A
authors.lastname: Neves
mesh_terms: D000085:Acetates / Q000494:pharmacology*; D000818:Animals; D017079:Exercise Tolerance / Q000187:drug effects* / Q000502:physiology; D007037:Hypothyroidism / Q000097:blood / Q000139:chemically induced / Q000188:drug therapy* / Q000503:physiopathology; D008713:Methimazole; D018482:Muscle, Skeletal / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects; D010472:Perchlorates; D010636:Phenols / Q000494:pharmacology*; D017208:Rats, Wistar; D017670:Sodium Compounds; D013550:Swimming; D037042:Thyroid Hormone Receptors beta / Q000819:agonists*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000008:administration & dosage / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D000085:Acetates; C413355:GC 1 compound; D010472:Perchlorates; D010636:Phenols; D017670:Sodium Compounds; D037042:Thyroid Hormone Receptors beta; D014284:Triiodothyronine; D008713:Methimazole; D013972:Thyrotropin; C031068:sodium perchlorate; D013974:Thyroxine