Focal degradation of cardiomyocyte ultrastructures and cytoplasm, their sequestration, and autophagy were found in Wistar rats with daunomycin-induced regenerative and plastic myocardial insufficiency starting from day 1 after cytostatic treatment. These changes were morphologically manifested in the formation of myelin-like structures, autophagosomes, and secondary lysosomes. Sequestration and partial autophagy of the cytoplasm in cardiomyocytes with diminished or blocked protein synthesis reflect cell regression or involution directed to the adjustment of the cytoplasm volume to functional state of the nucleus.