Abstract
In this work, the effect of thyroxine on energy and oxidative metabolism in the mitochondria of the rat heart was studied. Hyperthyroidism was observed in experimental animals after chronic administration of T4, which was accompanied by an increase in serum concentrations of free triiodothyronine (T3) and thyroxine (T4) by 1.8 and 3.4 times, respectively. The hyperthyroid rats (HR) had hypertrophy of the heart. In HR, there was a change in the oxygen consumption in the mitochondria of the heart, especially when using palmitoylcarnitine. The assay of respiratory chain enzymes revealed that the activities of complexes I, I + III, III, IV increased, whereas the activities of complexes II, II + III decreased in heart mitochondria of the experimental animals. It was shown that the level of respiratory complexes of the electron transport chain in hyperthyroid rats increased, except for complex V, the quantity of which was reduced. The development of oxidative stress in HR was observed: an increase in the hydrogen peroxide production rate, increase in lipid peroxidation and reduced glutathione. The activity of superoxide dismutase in the heart of HR was higher than in the control. At the same time, the activity of glutathione peroxidase decreased. The obtained data indicate that increased concentrations of thyroid hormones lead to changes in energy metabolism and the development of oxidative stress in the heart of rats, which in turn contributes to heart dysfunction.
Highlights
Thyroid diseases are among the most abundant endocrine pathologies in the world [1]
There was about a 1.8- and 3.4-fold increase in T3 and T4 levels in hyperthyroid rats (HR) compared with the values in the control group (Table 1)
The heart/body weight ratio increase in HR is indicative of significant T4 -induced cardiac hypertrophy (Table 1)
Summary
Thyroid diseases are among the most abundant endocrine pathologies in the world [1]. Some studies have shown that an increased concentration of thyroid hormones can induce mitochondrial biogenesis, enhancing the ability of cells to generate the energy necessary for biological processes [3,4,5]. It is known that there is a stimulation of the mitochondrial respiration rate of different organs [6,7,8] and a change in the activity of electron transport chain enzymes (ETC) [9]. The generation of reactive oxygen species may increase [9,10,11], lipid oxidation and lipid composition disorders may occur [3,12,13], and changes in antioxidant defense in different tissues may be induced [10,11,14]. There is neither a clear understanding of the changes nor assessment of the inhibiting and activating the enzymes both of the antioxidant system
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