Canine myocardial creatine kinase isoenzymes after chronic coronary artery occlusion

Creatine kinase (CK) exists as three cytosolic isoenzymes, CK-MM, CK-MB, and CK-BB, and one mitochondrial isoenzyme. Animal and human observations suggest that the CK-MB content of myocardium is dynamic and may increase in response to ischemia, but the response of the myocardial CK system to chronic coronary artery occlusion is not well-defined.

We measured serial changes in myocardial total CK, percent CK-MB, and percent CK-BB before and 3 weeks after coronary artery occlusion in 17 pentobarbital-anesthetized dogs. Tissue biopsies were obtained from the left anterior descending (LAD) coronary artery myocardium, the right coronary artery (RCA) myocardium, and the circumflex coronary artery myocardium at baseline and 3 weeks after LAD occlusion (n = 6), RCA occlusion (n = 5), and no coronary artery occlusion (n = 6). Tissue samples were assayed for total CK, percent CK-MB, and percent CK-BB. Samples were also examined by electron microscopy for evidence of ischemic myopathy. Total myocardial CK activity did not change over 3 weeks. Percent CK-MB increased significantly in the tissue supplied by the occluded artery (4.1-fold in dogs with LAD occlusion and 6.7-fold in dogs with RCA occlusion). Percent CK-BB did not change. Dogs with LAD occlusion had ultrastructural evidence of myopathic fibers interspersed with normal fibers in the LAD myocardium. Dogs with RCA occlusion had no ultrastructural evidence of myopathic fibers in the RCA myocardium.

Chronic coronary artery occlusion causes a pronounced change in the canine myocardial CK system that is limited to the tissue supplied by the occluded coronary artery. These biochemical alterations do not correlate with any cellular ultrastructural changes. Myocardial CK-MB content is dynamic, varies geographically within the heart, and increases rapidly after coronary artery occlusion.