Abstract:
Thyroid hormones have a significant impact on heart function through both genomicand non-genomic effects. Deficiency or excess of thyroid hormones leads to profoundchanges in the regulation of cardiac function and cardiovascular hemodynamics. Theheart is the main target organ for the action of thyroid hormones and in patients withhypo- or hyperthyroidism there are marked changes in the work of the heart. The aim ofthe work was to establish ultrastructural changes in myocardial components inexperimental hyperhomocysteinemia (HHCy) against the background of hyper- andhypothyroidism. Thiolactone HHCy was modelized by administering to animals anexogenous HCy in the form of thiolactone at a dose of 100 mg/kg body weight once aday for 28 days. Hyperthyroidism was modelized by daily administration of L-thyroxineat a dose of 200 μg/kg for the 21 days, hypothyroidism - daily administration of thiamazoleat a dose of 10 mg/kg for the 21 days. Individual groups of animals were administeredL-thyroxine and thiamazole in parallel with HCy. High levels of HCy adversely affectedthe walls of myocardial blood vessels. The lumens of hemocapillaries were plethoric,filled with erythrocytes. Changes in endotheliocytes were revealed, and cardiomyocytescontained deformed nuclei. In laboratory animals with hyperthyroidism, an increase inultrastructural changes in the walls of blood vessels (edema of the walls ofhemocapillaries, damaged cristae in mitochondria) were established. In animals thatwere modeled for hyperthyroidism and HHCy, more significant changes inendotheliocytes were revealed, most of the mitochondria were destroyed. Morepronounced alterative changes were revealed in cardiomyocytes. An electronmicroscopic examination of the myocardium of animals with hypothyroidism showedsignificant degenerative changes in the ultrastructure of the walls of blood vessels, andhypertrophied mitochondria were also found. The combined influence of hypothyroidismand HHCy caused the most profound disturbances in the ultrastructure ofcardiomyocytes and hemocapillaries in comparison with other groups of animals. Theintegrity of intercellular contacts was impaired, most of the mitochondria of myocyteshad destroyed cristae and the outer membrane
