[Ultrastructural organization of cardiomyocytes in various lower vertebrates].

Electron microscopy was used to study myocardium in Cyprinus carpio, Bufo bufo and Lacerta agilis. Myofibrils, mitochondria, nuclei and secretory granules in cardiomyocytes (CMC) of atrium and ventricle were analyzed quantitatively. Amphibians and reptiles showed significant complication of both structural organization of CMC and intercellular contacts versus bony fish. The absence of T-systems in bony fish was noted.