[Polyploidization of cardiac myocytes as a programmed event of ontogenesis]

The pieces of ventricles of newborn rats, which consist of diploid myocytes in more than 95%, were transplanted under the renal capsule of a syngeneic adult rat. Within 35 days the transplants contained 40 to 60% of the cells with the double or even greater DNA content in the mononuclear and binuclear classes. The composition of the classes was similar unlike the number of the cells of a certain class in the transplant and in the heart of a 35 day old rat. A conclusion has been drawn that the polyploidization is programmed and the realization of this programme depends on the growth, work, and other factors but is expressed even at their minimal action in the transplant. The growth of the transplanted myocytes was weaker than in the heart. It is supposed that, unlike the polyploidization, the growth of the myocytes outside the cycle is, predominantly, functional-dependent.