The development and distribution of binucleation in cardiac myocytes of different species.

Abstract

It has been observed that up to 80% of the muscle cells in the adult rat heart are binucleated. This observation was extended using the technique of nuclear counting in enzymatically dispersed myocytes from different regions and at different ages in the rat. About 80% of the myocytes thus obtained from the right ventricle and from different regions of the left ventricle of the adult rat were found to be binucleated. This level was reached by the fourteenth day of post-natal life. When changes in the rate of body and heart growth were induced in litters of different size, it was evident that the attainment of the adult proportion of binucleated myocytes was more closely related to body and heart weight than to age. In the beef heart, the overall proportion of binucleated myocytes was found to be 48%, with a uniform distribution in different regions. In the rabbit, dog and cat hearts, far lower percentages of binucleated cardiac muscle cells were observed in newborn and young animals than in adults of the given species.