DNA synthesis in rat atrial myocytes as a response to left ventricular infarction. An autoradiographic study of enzymatically dissociated myocytes.

An autoradiographic study was performed on enzymatically isolated atrial muscle cells to examine the DNA synthetic response of atria to left ventricular infarction. DNA synthesis was studied in left and right atrial myocytes and nonmyocytes of: young Sprague-Dawley rats 11 days after ligation of the left coronary artery; rats subjected to a sham surgical procedure without coronary artery ligation; unoperated rats. Each animal received a series of ten injections of tritiated thymidine at 12-h intervals, beginning on the fifth post-operative day; cells were isolated 36 h after the last injection. In infarcted animals, 37.1% of the left atrial myocytes were labeled and binucleated, and 6.5% were labeled and mononucleated; 13% of the right atrial myocytes were labeled and binucleated, while 12.7% were labeled and mononucleated. For both the left and right atria, the incidence of tritiated thymidine label in myocytes of the sham-operated group was similar to that of the unoperated controls, indicating that the surgical procedure did not stimulate DNA synthesis in atrial myocytes. In both left and right atria of the infarcted group, non-muscle cells were labeled to a greater extent (49.9% and 47.1%) than in the sham-operated group (22% and 20.8%), which in turn showed labeling to a greater extent than did the unoperated control group (10.9% and 11.6%), indicating that DNA synthesis was stimulated in non-myocytes of the atria by the sham operation and was further stimulated by experimental infarction.(ABSTRACT TRUNCATED AT 250 WORDS)