Exercise training increases creatin kinase capacity in canine myocardium

Introduction: The creatine kinase (CK) energy shuttle of cardiomyocytes channels metabolic energy from the mitochondria to sites of energy utilization at contracting myofibrils and sarcolemmal and sarcoplasmic reticular ion pumps. Although plasticity of the myocardial CK system in response to hemodynamic overload has been repeatedly demonstrated, the effects of aerobic exercise training on myocardial CK are less well understood. This investigation tested the hypothesis that aerobic exercise training increases the capacity of the CK system in canine myocardium. Methods: Mongrel dogs were conditioned by a 9-wk treadmill running program or cage-rested for 4 wk. Total CK activity was measured colorimetrically; CK_MB was separated from other CK isoforms and measured by electrophoresis. Results: Relative to sedentary controls, training increased left ventricular total CK activity 46% (P <0.05) but did not alter total CK activity in right ventricular myocardinm. Also in left ventricular myocardium, training increased CK_MB isoenzyme activity 4.5-fold and the CK_MB fraction of total CK threefold from 1.1 ± 0.4 to 3.4 ± 0.8% (P <0.05). In contrast to left ventricle, CK_MB activity and its fraction of total CK activity were not altered by training in right ventricular myocardium. Conclusions: Aerobic exercise training increases total myocardial CK activity and CK_MB content in canine left ventricular myocardium, although CK_MB remains a minor component of the myocardial CK system. The right ventricular CK system was not affected by training.