RESUMEN
OBJECTIVE: Introduction: There is an increasing number of cases of congenital hypothyroidism. One of the most common complications of hypothyroidism is damage to the cardiovascular system, which in 30-50% of patients leads to the development of arterial hypertension. The aim: studying the features of the ultrastructure of myocardial capillaries in mature rats with hypothyroidism. PATIENTS AND METHODS: Materials and methods: Experiments were conducted on 40Wistar line rats with congenital hypothyroidism: juvenile young (45-day) and sexually mature (100-day) rats, as well as intact animals of the corresponding age. While extracted from the experiment rats of all experimental groups had their arterial pressure measured using a plethysmograph while the development of hypothyroidism was controlled by the immune-enzymatic method. Electron microscopic examination of the left ventricular myocardium and morphometric study of volumetric and quantitative densities, cross-section area, and form factor of micropinocytotic vesicles were conducted. RESULTS: Results: In the sexually mature rats with congenital hypothyroidism the quantitative density of the capillaries in the myocardium decreases. Activation of transcytosis is accompanied by significant violations of vesiculation. Some of the endothelial cells of experimental animals contain a moderate amount of transport vesicles, while others are overfilled with these structures and desquamate into the lumen. In older rats with congenital hypothyroidism there is a further dilution of capillaries, the development of hypoxic state in them, mucinous edema of interstitial space, decrease of biosynthetic and transport processes activity. CONCLUSION: Conclusions: In young (45-day) rats with congenital hypothyroidism the direction and expressiveness of compensatory processes is to enhance the transcytosis processes. Dystrophicdestructive changes are manifested by apoptosis in some endothelial cells, decrease in the number of biosynthetic organelles, lysis and edema of their cytoplasm. In sexually mature (100-day) rats with congenital hypothyroidism destructively-dystrophic processes in the blood capillaries of the myocardium are approximately balanced with compensatory-adaptive.
