Changes in DNA content, number of nuclei and cellular dimensions of young rat atrial myocytes in response to left coronary artery ligation.
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abstract
Studies of enzymatically isolated myocytes from atria of young male Sprague-Dawley rats at 11 days after left coronary artery ligation show that a major response of atrial myocytes to ventricular infarction is binucleation. In sham-operated animals, 23.2% of left and 15.5% of right atrial myocytes were binucleated, compared to 77.8% of left and 40.5% of right atrial myocytes of infarcted animals. Examination of 150 g and 250 g unoperated control animals indicate that this response is occurring at a time when a small but significant amount of binucleation is also occurring as a normal part of growth. Using a Feulgen-acriflavine-SO2 method for cytofluorometry, a significant increase in ploidy was seen in left atrial myocytes of infarcted animals over those of sham or control animals. The number of left atrial myocytes in infarcted animals having a ploidy level above 3C was 10.8% above sham values. The mean length of binucleated myocytes of left atrium was significantly greater in infarcted animals (119.8 microns) than in sham-operated animals (97 microns) and the mean length of mononucleated myocytes was greater in infarcted animals (104.1 microns) than in sham-operated animals (77 microns). Thus, cardiac myocytes are capable of a substantial response to a stressful situation by increases in cell length, number of nuclei and ploidy. Study of a model system such as the rat atrium may yield an understanding of the mechanisms involved in the induction of these nuclear changes.
