Alterations of substances (DNA, myoglobin, myosin, protein) in experimentally induced cardiac hypertrophy and under the influence of drugs (isoproterenol, cytostatics, strophanthin)

Summary

In growing human hearts the biochemically estimated total amount of DNA increases from 20 mg to 50–100 mg, and in hypertrophied hearts the increase may be threefold compared with normal hearts. Whereas most animal hearts have nearly only diploid muscle cells, in human hearts most muscle cell nuclei are polyploid. According to the grade of hypertrophy a pronounced polyploidisation of heart muscle cells occurs. The quantitative ratio of noncondensed chromatin/condensed chromatin remains constant 4:1 in all grades of hypertrophy. The amount of myoglobin in hearts above 500 g weight is more than 100% compared with normal hearts and is correlated with the width of the heart muscle fibres. In hypertrophied hearts an irregular and higher double refraction of myosin can be seen indicating an early stage of necrosis. In concentric cardiac hypertrophy the dry weight of the muscle fibres is more increased than in eccentric hypertrophy. The protein concentration within the muscle fibres increases with rising heart weight. Some cytostatics cause a decrease of the myocardial DNA content, a reduction of the ploidy level and a diminishing of the number of connective tissue cells. Isoproterenol effects, within the first 3 weeks after administration, a severe reduction of the cell number; after 2 months a pronounced polyploidisation of the heart muscle cells occurs and the cell number increases again above the normal level indicating the regeneration capabilities of the myocardium.