Depressed Myocardial Creatine Phosphokinase Activity Following Experimental Myocardial Infarction in Rabbit

Since creatine phosphokinase (CPK) is found predominantly in myocardial and skeletal muscle cells, in contrast to cells participating in the inflammatory response, it was considered likely that measurement of activity of this enzyme in the heart would provide a sensitive and relatively specific index of the extent of ischemic injury following acute coronary artery occlusion. Accordingly, CPK activity was measured serially following coronary artery occlusion in extracts from rabbit myocardium with gross infarction and from normal rabbit left ventricle. In addition, myocardial CPK activity was assayed in extracts from various portions of dog hearts 24 hours after ligation of the coronary artery. CPK activity of rabbit myocardium with infarction was uniformly depressed within 6 hours following coronary occlusion. After 24 hours, activity declined from 15.5±0.9 (mean±SE) to 3.4±0.3. CPK activity in whole left ventricular extracts was depressed and in general, the extent of depression was proportional to the size of the gross infarct. CPK depression in various regions of the dog heart 24 hours after coronary occlusion correlated with the extent of reduction of blood flow determined with the use of radioactively labeled microspheres. Results suggest that depression of myocardial CPK activity may be useful in estimating the extent of tissue damage following experimental coronary artery occlusion and the effect of prophylactic and therapeutic measures on the survival of myocardium in this setting.