[Activation of rat heart atrial and auricular cells after left ventricular infarct]

The number of the DNA-synthesizing nuclei in the connective tissue cells of the auricle and the auricula atril rose from the 1st to the 15th day after the experimental induction of left ventricular infarction in rats. In the myocytes of the auricula atril the amount of the labeled nuclei peaked on the 5th day, and that of mitoses--on the 7th day. In myocytes of the auricle the number of the nuclei incorporating 3H-thymidine was insignificant and only occasional abnormal mitoses were observed. In the rat hearts with healed infarctions the amount of polyploid nuclei was increased both in the myocytes of the auricle and of the auricula atrii.