[Secretory granules in cardiomyocytes]

The specific granules having the appearance of spherical formations of 2000-4000 A in diameter are described in the cardiocytes of the atria and ventricles of mature frogs (R. temporaria). Each granule consists of electron dense granular matrix and a membrane up to 60 A trick. The amount of these granules in the cardiomyocytes of the atria is greater and they occasionally form accumulations, connected as a rule with the elements of the lamellar complex. The rough reticulum is better developed in the cells containing clusters of granules. The granules described are considered to be secretory ones.