RESUMEN
The study examined the myocardial ultrastructural alterations in rats maintained on various atherogenic diets. It revealed the complex ultrastructural alterations of cardiomyocytes and endotheliocytes (including the lytic and destructive changes of the intracellular organelles, upregulation of the autophagocytosis in the cardiomyocytes, and necrobiosis with apoptosis of endotheliocytes) reflecting the cytopathic features of circulating cholesterol and lipoproteins, whose elevation determined the intensity of destructive processes. The revealed peculiarities in the changes of lipid inclusions (their osmiophilic transformation) in cardiomyocytes can be provoked by entry of cholesterol into the cells and its further metabolic modifications. During moderate dyslipidemia, the cardiomyocytes demonstrated the ultrastructural signs of induction of intracellular regeneration (marked with the clusters of polysomes in the intermyofibrillar and subsarcolemmal spaces with appearance of neogenic myofilaments) and upregulated pinocytotic activity. In all cases, up-regulated autophagocytosis in cardiomyocytes was accompanied by accumulation of myelin- and vacuole-like structures in the intercellular spaces and capillary lumens paralleled with appearance of activated forms of macrophages and fibroblasts in the myocardium.