[Age changes in properties of myofibrillary creatine phosphokinase enzyme in the rat myocardium during stress]

The activity of the myofibrillar isoenzyme creatine phosphokinase (CPK) in the heart inhibits with age. This may be explained by impaired association of CPK with myofibrils. The immobilization stress led to a sharp fall in CPK activity in its decreased affinity to the substrate. Changes in the catalytic properties of myofibrillar CPK in the myocardium of adult stressed rats raise effectiveness of its function in altered cardiac metabolism in stress.