title: Exercise training increases creatine kinase capacity in canine myocardium.
abstract: BACKGROUND
  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 myocardium. 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.
authors.affiliation: Department of Integrative Physiology and the Cardiovascular Research Institute, University of North Texas Health Science Center at Fort Worth, 76107-2699, USA.
authors.forename: S R
authors.initials: SR
authors.lastname: Stuewe
authors.forename: P A
authors.initials: PA
authors.lastname: Gwirtz
authors.forename: R T
authors.initials: RT
authors.lastname: Mallet
mesh_terms: D000818:Animals; D003402:Creatine Kinase / Q000378:metabolism*; D004285:Dogs; D006352:Heart Ventricles / Q000201:enzymology*; D009206:Myocardium / Q000201:enzymology*; D010805:Physical Conditioning, Animal / Q000502:physiology*; D014481:United States
chemical_list: D003402:Creatine Kinase