title: Short-term thyroid hormone excess affects the heart but does not affect adrenal activity in rats.
abstract: BACKGROUND
  Hyperthyroidism (Hy) exerts a broad range of influences on a variety of physiological parameters. Its disruptive effect on cardiovascular system is one of its most remarkable impacts. Moreover, Hy has been clinically associated with stress - induced hyperactivation of the hypothalamic-pituitary-adrenal axis.
  
  
  OBJECTIVE
  Evaluate the impact of short-term Hy on cardiac performance and adrenal activity of rats.
  
  
  METHODS
  Induction of Hy in Wistar rats through injections of T3 (150 µg/kg) for 10 days (hyperthyroid group - HG) or vehicle (control group). The cardiovascular performance was evaluated by: echocardiography (ECHO); heart weight/body weight (mg/gr) ratio; contractility of isolated papillary muscles (IPM) and direct measurement of blood pressures. Adrenal activity was evaluated by adrenal weight/body weight (mg/gr) ratio and 24-hour fecal corticosterone (FC) levels on the, 5th and 10th days of T3 treatment.
  
  
  RESULTS
  In HG, the ECHO showed reduction of the End Systolic and End Diastolic Volumes, Ejection, Total Diastolic and Isovolumic Relaxation Times, Diastolic and Systolic Areas and E/A ratio. Heart Rate, Ejection Fraction and Cardiac Output increased. The heart weight/body weight ratio was higher. Similarly, in IPM, the maximum rate of force decay during relaxation was higher in all extracellular calcium concentrations. Systolic blood pressure (SBP) levels were higher. (p ≤ 0.05). On the other hand, there was no difference in the adrenal weight/body weight ratio or in the 24-hour FC levels.
  
  
  CONCLUSIONS
  Hy induces positive inotropic, chronotropic and lusitropic effects on the heart by direct effects of T3 and increases SBP. Those alterations are not correlated with changes in the adrenal activity.
authors.affiliation: Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: Ariani Cavazzani
authors.initials: AC
authors.lastname: Szkudlarek
authors.affiliation: Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: Bruno
authors.initials: B
authors.lastname: Aldenucci
authors.affiliation: Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: Nelson Itiro
authors.initials: NI
authors.lastname: Miyagui
authors.affiliation: Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: Ilana Kassouf
authors.initials: IK
authors.lastname: Silva
authors.affiliation: Pontifícia Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: Rosana Nogueira
authors.initials: RN
authors.lastname: Moraes
authors.affiliation: Universidade Federal da Bahia, Salvador, BA, Brasil.
authors.forename: Helton Estrela
authors.initials: HE
authors.lastname: Ramos
authors.affiliation: Universidade Federal do Paraná, Curitiba, PR, Brasil.
authors.forename: Rosalva Tadeu Hochmuller
authors.initials: RT
authors.lastname: Fogaça
mesh_terms: D000311:Adrenal Glands / Q000503:physiopathology*; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D003345:Corticosterone / Q000032:analysis; D004195:Disease Models, Animal; D004452:Echocardiography; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology; D006980:Hyperthyroidism / Q000150:complications* / Q000503:physiopathology*; D008297:Male; D010210:Papillary Muscles / Q000503:physiopathology; D010913:Pituitary-Adrenal System / Q000503:physiopathology*; D017208:Rats, Wistar; D012016:Reference Values; D013974:Thyroxine / Q000032:analysis; D013997:Time Factors; D014284:Triiodothyronine / Q000032:analysis
chemical_list: D014284:Triiodothyronine; D013974:Thyroxine; D003345:Corticosterone