Mitosis of Heart Muscle Cells in Normal Rats

In order to demonstrate mitotic figures of the heart muscle cells and the interstitial cells during normal growth, colchicine was given to a total of 20 rats of various ages and mitosis in the myocardial cells was evaluated. The mitotic rate of heart muscle cells in 4 hours was 1.9-2.1% on the first day of life and it gradually decreased to 0.1% in 4 weeks and zero thereafter. The mitotic rate of interstitial cells was 2.0-2.2% on the first day of life and it similarly decreased to 0.1% in 6 months. These results seem to support our view that heart muscle cells and interstitial cells divide and increase in number with postnatal growth of the heart.