Relationship between deoxyribonucleic acid content and nucleoli in human heart muscle cells and estimation of cell number during cardiac growth and hyperfunction.

In the myocardium of 30 human hearts of all age groups quantitative deoxyribonucleic acid (DNA) measurements were performed and the results of the measurements were correlated with the pure myocardium weight. By means of the diphenylamine reaction the total amount of DNA (DNA concentration and DNA amount) in the myocardium was estimated. By means of Feulgen cytophotometry the DNA amount exclusively in the heart muscle cell nuclei was measured. With the use of myocardial tissue spread on slides, the nuclear areas of the heart muscle nuclei were planimetrically measured. After preparation with DNase and staining with gallocyanine chromalumn the nucleoli in heart muscle nuclei were specifically presented and their number per nucleus as well as their area values were demonstrated. From the biochemical and cytophotometric results of the myocardial DNA content it was possible to estimate the absolute cell number of the hearts, keeping the pure myocardium weight in consideration. The investigations led to the following results. In growing childrens' hearts the DNA concentration decreases to a constant level of 0.3-0.4 mg/g. The amount of DNA rises with increasing heart weight. During the growth of the heart of a child between the ages of 8 and 12 the DNA amount doubles in the heart muscle nuclei, and most of the muscle nuclei of an adult have a tetraploid DNA content. In pathological heart hypertrophy a further polyploidization of the heart muscle nuclei occurs. The areas of the nuclei increases with growing polyploidization. The nuclear areas form the same grouping as the ploidy classes. With growing nuclear areas, the total areas of the nucleoli and their number per nucleus also increase. Right after birth an increase in the number of connective tissue and heart muscle cells follows. A normal heart contains about 2 x 10(9) muscle cells. In hypertrophic hearts the number of muscle cells can double.