Differential changes in the properties of mitochondrial isoenzyme creatinekinase from heart of adult and old rats during stress

We compared the effects of immobilization stress on the properties of mitoc hondrial creatine kinase (CK) isoenzyme from the myocardium of adult and ol d rats. Here we show that the activity of CK in the myocardium of old rats is lower in comparison to that in the myocardium of adult ones. During stre ss, CK activity in the myocardium of old rats increases, whereas in the myo cardium of adults it does not. CK from the myocardium of adult rats is more sensitive to the modulating action of low pH, osmolarity, and Ca2+ concent rations than that of old rats. (C) 1999 Elsevier Science Inc. All rights re served.