Adenine Nucleotide and Creatine Phosphate Pool in Adult and Old Rat Heart during Immobilization Stress

<i>Background:</i> Disturbances in the heart energy provision is important in the stress-induced injury of myocardium. In order to learn the causes of age-dependent differences in myocardial sensitivity to stress, we determined the level of adenylates, creatine and creatine phosphate in adult and old rat heart during an immobilization stress. <i>Methods: </i>Fifty male Wistar rats were used to study the myocardial adenine nucleotides, creatine and creatine phosphate pool and creatine kinase activity during an immobilization period. <i>Results: </i>The concentration of adenine nucleotides in old and adult rat hearts was similar. The total concentration of adenylate pool, ATP and ADP in the heart of both age groups was reduced during stress. However, in old rats under stress the concentration of ATP in a less measure and ADP in a greater measure is decreased against that observed in adult animals. The level of inorganic phosphate in old rat heart remains the same as in adult rats. <i>Conclusion: </i>The creatine kinase system may be important in stabilizing the ATP level in myocardium of adult rats during stress. The role of this system in heart energy metabolism during stress is decreased in old rats. Disturbances of isoenzyme creatine kinase activity are responsible for these disorders.