Different response of cellular dna content to cardiac hypertrophy in human and rat heart myocytes

Abstract

1. 1. Rat and human heart myocytes adapt to overload-induced hypertrophy differently. 2. 2. Human myocyte nuclei respond with polyploidization and multinucleation, thus increasing the DNA content per myocyte from 20 to 40 pg. As a result, nuclear DNA content per 10,000 μm 3 of cell volume decreases from 12 to 10 pg. 3. 3. In rat hearts with aortic constriction nuclear DNA content remains constant (13 pg), and the DNA content per 10,000 μm 3 of myocyte volume falls from 9 to 6 pg. 4. 4. We hypothesize that “dilution” of nuclear DNA in the hypertrophied rat heart myocyte limits the capacity to hypertrophy (⪡100%). 5. 5. The human heart myocyte, which is able to compensate for dilution of nuclear DNA, may increase in size more than three-fold. 6. 6. The lower limit of DNA content per unit of myocyte volume is 6pg/10,000 μm 3 in both species.