title: Nitric oxide synthase activity in hyperthyroid and hypothyroid rats.
abstract: OBJECTIVE
  Thyroid disorders are accompanied by important changes in haemodynamic and cardiac functions and renal sodium handling. Since nitric oxide (NO) plays a crucial role in regulating vascular tone and renal sodium excretion, the present paper was designed to determine whether changes in the activity of NO synthase (NOS) participate in the cardiovascular and renal manifestations of thyroid disorders.
  
  
  METHODS
  We measured NOS activity in the heart (left and right ventricles), vessels (aorta and cava) and kidney (cortex and medulla) of euthyroid, hyperthyroid and hypothyroid rats after 6 weeks of treatment. NOS activity was determined by measuring the conversion of L-[(3)H]-arginine to L-[(3)H]-citruline.
  
  
  RESULTS
  NOS activity was higher in all tissues from hyperthyroid rats when compared with controls, except in the right ventricle. In the hypothyroid group, NOS activity showed a more heterogeneous pattern, with significant increases in both ventricles but significant reduction in the aorta, while in the vena cava, renal cortex and medulla the enzyme activity also tended to be higher, but significance was not reached.
  
  
  CONCLUSIONS
  These data indicated that NOS activity was upregulated in tissues primarily related to blood pressure control in hyperthyroid rats, suggesting that an increased NO production may contribute to the hyperdynamic circulation in hyperthyroidism and may have a protective homeostatic effect in the target organs of the hypertension that accompanies this endocrine disease. The aortic and renal findings in hypothyroid rats suggested a possible role for NOS in the increased peripheral resistance and the normal pressure-diuresis-natriuresis response of these hypotensive animals, although hypothyroidism produced a heterogeneous tissue response in NOS activity.
authors.affiliation: Departamento de Fisiología de la Facultad de Medicina de Granada, Granada, Spain.
authors.forename: Andrés
authors.initials: A
authors.lastname: Quesada
authors.forename: Juan
authors.initials: J
authors.lastname: Sainz
authors.forename: Rosemary
authors.initials: R
authors.lastname: Wangensteen
authors.forename: Isabel
authors.initials: I
authors.lastname: Rodriguez-Gomez
authors.forename: Félix
authors.initials: F
authors.lastname: Vargas
authors.forename: Antonio
authors.initials: A
authors.lastname: Osuna
mesh_terms: D000818:Animals; D001011:Aorta / Q000201:enzymology; D001120:Arginine / Q000493:pharmacokinetics; D001921:Brain / Q000201:enzymology; D002956:Citrulline / Q000493:pharmacokinetics; D006980:Hyperthyroidism / Q000201:enzymology*; D007037:Hypothyroidism / Q000201:enzymology*; D007668:Kidney / Q000201:enzymology; D008297:Male; D009206:Myocardium / Q000201:enzymology; D019001:Nitric Oxide Synthase / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D014316:Tritium; D014684:Venae Cavae / Q000201:enzymology
chemical_list: D014316:Tritium; D002956:Citrulline; D001120:Arginine; D019001:Nitric Oxide Synthase