Loss of myocardial CK-MB into the circulation following 3.5 hours of swimming in a rat model

The purpose of this study was to document alterations of creatine kinase-B (CK-B) in the left and right ventricles of rats and CK-MB release into the circulation following a single bout of stressful prolonged intense exercise. Male Sprague-Dawley rats, with 8% bodyweight attached to each tail, were forced to swim 3.5 hours and were then sacrificed immediately (0 h PS), 3 hours (3 h PS), 24 hours (24 h PS), and 48 hours (48 h PS) post swimming, respectively. Sedentary (control) rats were sacrificed at rest. Serum CK-MB mass increased 2.1 times (8.9 mug/L; p<0.01 vs. controls of 4.3 <mu>g/L) and 1.4 times (6.0 mug/L; P<0.01 vs, controls) at 0 h PS, and 3 h PS, respectively, and returned to baseline at 24 h PS. Western blot analysis indicated that CK-B of the right ventricle decreased 14% (p<0.05), 20% (p < 0.01), and 12% (p < 0.05) at 3 h PS, 24 h PS and 48 h PS, respectively. The CK-B of the left ventricles decreased 34% (p<0.05) at 0 h PS, returned to baseline at 3 h PS, and was increased 39% (P < 0.01) at 48 h PS. Our findings demonstrate that a single bout of stressful, prolonged, intense exercise resulted in CK-B subunit loss from the myocardium, resulting in increased serum CK-MB concentrations, an indication of myocardial injury.