[Ultrastructure of the subendocardiac cardiomyocytes of the dog heart in acute experimental myocardial infarct].

Experimental myocardial infarction was reproduced in large random-bred dogs by ligation of the left descending coronary artery. After 24 hours of ischemia, subendocardial Purkinje cells showed accumulations of lipid drops, development of foci of myofibril overcontraction with simultaneous accumulation in the cells of large lysosomes, disappearance of the external layer of sarcolemma, thinning of glycocalyx, and intact plasmalemma. Most contractile cardiomyocytes were changed irreversibly. Among them, however, there was a portion of viable cells with marked signs of lipid infiltration. These contractile cells lacked the external layer of sarcolemma, had thinned glycocalyx, plasmalemma in a number of cases was penetrable for colloid lanthanum. The ischemized cells with maximally thinned external layers of sarcolemma and intact plasmalemma may apparently be regarded as potential sources of ectopic activity. Overcontracted Purkinje cells are primarily among them.U