Ultrastructure of the contractile apparatus in cardiomyocytes during regenerative and plastic insufficiency of the myocardium.

Abstract

Lytic changes in cardiomyocyte myofibrils constituting the morphological basis of contractile insufficiency were found in Wistar rats with regenerative and plastic myocardial insufficiency 3 h after daunomycin administration. Myofibrils became less dense, empty spaces appeared in many sarcomeres, sometimes total lysis of myofilaments within the sarcomere was noted. These changes were most pronounced in the perinuclear zone. Intracellular regeneration of cardiomyocytes was characterized by disorientation of newly formed myofibrils in relation to the long axis of muscle fibers and preserved myofibrils. Progressive inhibition of protein synthesis, lysis of myofibrils, and focal degradation of the sarcoplasm caused apoptotic death of some cardiomyocytes.