. Postnatal hypothyroidism : alterations in nitric oxide system in left ventricle cardiomyocites.

ABRAMOVICI BLASCO, VAZQUEZ F, LISTA F, ARRECHE N, BALASZCZUK A, FELLET A.

Congreso; LXIV Reunión Anual de la Sociedad de Investigación Clínica; 2019

We previously demonstrated that hypothyroidism reduced cardiac contractility decreasing Ca2+ transient amplitude and sarcoplasmic-reticulum Ca2+ content in isolated cardiomyocytes. This negative inotropic effect was associated with an increased cardiomyocyte relaxation as revealed by a reduction in the time to 50% relengthening. The aim of this study was to examine whether this cardiac involves changes in left ventricle nitric oxide system, caveolins 1/3 and /or Akt protein levels. Male Sprague?Dawley rats weighing approximately 50 g were randomly assigned to one of the two experimental groups: (1) euthyroid rats (received SC injections of 0.9 NaCl (0.1 ml/100 g body weight) or (2) hypothyroid rats (received 0.02% methimazole in drinking water during 60 days). Heart function was evaluated by echocardiography. Measurements of arterial blood pressure, heart rate, nitric oxide synthase (NOS) activity and protein levels were performed. Hypothyroid animals had decreased fractional shortening and ejection fraction and increased left ventricle internal diameter. While perinatal hypothyroidism increased total NOS activity, the protein levels of the different isoenzymes were not modified. Both total Akt and phosphorylated Akt protein levels were increased in hypothyroid rats. Caveolin-1 and 3 protein content were not affected by the treatment. We speculate that the reduction in contractility and relaxation time observed in hypo rats might be attributed to the increase in NO production, explaining the decrement of the EF observed in hypo rats. Akt pathway could be related to the rise of NO synthase activity, altering cardiac function during this thyroid disorder.