Age-related changes in ploidy levels and biochemical parameters in cardiac myocytes isolated from spontaneously hypertensive rats.

Postnatal growth of the mammalian ventricular myocyte is characterized by a brief period of hyperplasia followed by an extensive period of physiological hypertrophy. Using myocytes isolated from both Wistar-Kyoto and spontaneously hypertensive rats from fetus to 10 months old, we analyzed morphological, biochemical, and ploidy changes. Fetal myocytes from both spontaneously hypertensive and Wistar-Kyoto rats were mononuclear, diploid cells. By 4 weeks, adult binucleation levels (84% binuclear) were found, and myocytes pooled from both ventricles demonstrated nuclear ploidy shifts to tetraploid levels. However, analysis of myocytes isolated from left ventricle, right ventricle, and septum showed that nuclear polyploidation was confined to the right ventricle and septum, with few polyploid nuclei detected in the left ventricle. This pattern remained relatively constant through 10 months of age, although spontaneously hypertensive myocytes showed significantly more polyploidation than Wistar-Kyoto in all reg...