Increased resistance to fatigue in creatine kinase deficient muscle is not due to improved contractile economy.
There has been speculation on the origin of the increased endurance of skeletal muscles in creatine kinase (CK)-deficient mice. Important factors that have been raised include the documented increased mitochondrial capacity and alterations in myosin heavy chain (MyHC) isoform composition in CK-deficient muscle. More recently, the absence of inorganic phosphate release from phosphocreatine hydrolysis in exercising CK-deficient muscle has been postulated to contribute to the lower fatigueability in skeletal muscle. In this study, we tested the hypothesis that the reported shift in MyHC composition to slower isoforms in CK-deficient muscle leads to a decrease in oxygen cost of twitch performance. To that aim, extensor digitorum longus (EDL) and soleus (SOL) muscles were isolated from wild-type (WT) and knock-out mice deficient in the cytoplasmic muscle-type and sarcomeric mitochondrial isoenzymes of CK, and oxygen consumption per twitch time-tension-integral (TTI) was measured. The results show that the adaptive response to loss of CK function does not involve any major change to contractile economy of skeletal muscle.
Department of Experimental In Vivo NMR, Image Sciences Institute, University Medical Center Utrecht, Utrecht, The Netherlands. frank.terveld@ddz.uni-duesseldorf.de
Frank
F
ter Veld
Klaas
K
Nicolay
Jeroen A L
JA
Jeneson
D000818:Animals; D001696:Biomechanical Phenomena; D003402:Creatine Kinase / Q000172:deficiency*; D006146:Guanidines; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology; D018656:Muscle Fibers, Fast-Twitch / Q000378:metabolism; D018657:Muscle Fibers, Slow-Twitch / Q000378:metabolism; D018482:Muscle, Skeletal / Q000378:metabolism*; D018995:Myosin Heavy Chains / Q000378:metabolism; D010101:Oxygen Consumption / Q000502:physiology*; D011422:Propionates; D020033:Protein Isoforms
D006146:Guanidines; D011422:Propionates; D020033:Protein Isoforms; D003402:Creatine Kinase; D018995:Myosin Heavy Chains; C005775:guanidinopropionic acid