Polyploidy in the myocardium and compensatory reserve of the heart

The mammalian heart is a polyploid organ. Cardiac myocytes undergo polyploidization in the early postnatal ontogeny, and the degree of their polyploid depends on the conditions of heart growth. The myocardium of healthy persons is characterized by considerable individual variability of polyploidy. The principal mechanism by which normal and compensatory growth of the heart occurs in adult mammals is through increases of cytoplasmic mass in postmitotic myocytes. In the normal myocardium, the protein mass of myocytes does not correspond to the gene dosage, while their protein mass in a hypertrophic myocardium becomes a multiple of their ploidy. The capacity of polyploid myocytes to grow so as to double their mass constitutes the reserve of cardiac growth. This reserve, which is laid down in the early ontogeny, materializes in response to functional overloading of the heart in adult life. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 119, N ^o 5, pp. 454–459, May, 1995 Presented by D. S. Sarkisov, Member of the Russian Academy of Medical Sciences