Faster O2 Uptake Kinetics in Canine Skeletal Muscle in Situ after Acute Creatine Kinase Inhibition

The ability to sustain skeletal muscle contractions is dependent on the conversion of chemical to mechanical energy – a process fueled by adenosine triphosphate (ATP). The link between two of the major mechanisms for ATP provision, phosphocreatine (PCr) breakdown and oxidative phosphorylation, was investigated in canine muscle. Infusion of a drug to prevent PCr breakdown (via inhibition of the enzyme creatine kinase; CK) caused (among other effects) a faster adjustment of energy provision from oxidation upon the onset of contractions. Thus, in mammalian skeletal muscle the CK enzyme slows the signal responsible for the activation of oxidative phosphorylation. Sudden increases in the demands for energy at the onset of exercise are met by PCr breakdown, but this process is functionally related, presumably through the levels of some of its metabolites, to the regulation of oxidative phosphorylation, the most important pathway for ATP resynthesis.