DNA AND PROTEIN RELATIONS IN CARDIOMYOCYTES - GROWTH RESERVE IN CARDIAC-MUSCLE

Two-wavelength scanning cytophotometry was performed for the measureme nt of DNA (Feulgen reaction) and total protein content (naphtol yellow S staining) in the same cardiac myocyte. A lack of proportionality be tween the DNA content (i.e, cell ploidy) and protein content has been detected in ventricles of normal weight in the human heart. While the ploidy classes contained ratios of 2:4:8:16:32, the ratio of the prote in content was about 2:3:5:8:17. In hypertrophic left or right ventric les, the latter ratio composed a series of doubling. Owing to this add itional growth, weight of muscle tissue may be increased from 30% to t wice, depending on the myocyte ploidy of a given myocardium which vari es from 4 to 10c on average under normal circumstances and to 30c in s ome cases of hypertrophy (where c is the haploid DNA content, and, acc ordingly, a haploid chromosome set). Thus, one of the mechanisms of ca rdiac hypertrophy has been revealed which comprises the first step of the growth and often the process per se. Polyploidization of cardiac m yocytes and their postmitotic growth enhance the heart weight in norma l circumstances and creates a growth reserve for hypertrophy under con ditions of pathology in future.