[Proliferation of the myoctes of the left atrium and ventricle after different kinds of myocardial injuries in adult rats].

Myocardial infarction of the left ventricle was induced in adult rats weighing 120-160 g by ligation of the left coronary artery at various levels: in the area of the auricle, of the first third of the left ventricle, and in the middle of it. The left auricle was injured in the other experimental series: the ligature was applied to its anterior wall or to the auricular appendage. Sham-operated animals served as control; only pericardium was removed in them. The left half of the heart was examined on the 5th postoperative day. Mitosis of myocytes was found in the auricle or in the auricular appendage of the animals in those experimental series in which these sections of the heart were injured directly and had a thickened epicardium (in 35 of 49 cases); mitotic index varied from 0.9 to 10%. No mitoses were found in the myocytes of the auricle and the auricular appendage after ligation of the coronary artery in the middle of the ventricle. Mitoses in the myocytes of the ventricle were rare (in 7 of 49 cases) and were located far from the site of infarction, in the subepicardial region; mitotic index here varied from 1 to 2%.