Biomaterial Database

Muscle fatigue: the role of intracellular calcium stores. 2002

David G Allen, and Akram A Kabbara, and H kau Westerblad

Department of Physiology, University of Sydney F13, NSW 2006, Australia.

Force declines when muscles are used repeatedly and intensively and a variety of intracellular mechanisms appear to contribute to this muscle fatigue. Intracellular calcium release declines during fatigue and has been shown to contribute to the reduction in force. Three new approaches have helped to define the role of calcium stores to this decline in calcium release. Skinned fibre experiments show that when intracellular phosphate is increased the amount of Ca2+ released from the sarcoplasmic reticulum (SR) declines. Intact fibre experiments show that the size of the calcium store declines during fatigue and recovers on rest. Intact muscles which lack the enzyme creatine kinase, do not exhibit the usual rise of phosphate during fatigue and, under these conditions, the decline of Ca2+ release is absent or delayed. These results can be explained by the "calcium phosphate precipitation" hypothesis. This proposes that if phosphate in the myoplasm rises, it enters the SR and binds to Ca2+ as Ca2+ phosphate. The resultant reduction in free Ca2+ within the SR contributes to the reduced Ca2+ release during fatigue.

UI	MeSH Term	Description	Entries
D010710	Phosphates	Inorganic salts of phosphoric acid.	Inorganic Phosphate,Phosphates, Inorganic,Inorganic Phosphates,Orthophosphate,Phosphate,Phosphate, Inorganic
D002118	Calcium	A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol Ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes.	Coagulation Factor IV,Factor IV,Blood Coagulation Factor IV,Calcium-40,Calcium 40,Factor IV, Coagulation
D003402	Creatine Kinase	A transferase that catalyzes formation of PHOSPHOCREATINE from ATP + CREATINE. The reaction stores ATP energy as phosphocreatine. Three cytoplasmic ISOENZYMES have been identified in human tissues: the MM type from SKELETAL MUSCLE, the MB type from myocardial tissue and the BB type from nervous tissue as well as a mitochondrial isoenzyme. Macro-creatine kinase refers to creatine kinase complexed with other serum proteins.	Creatine Phosphokinase,ADP Phosphocreatine Phosphotransferase,ATP Creatine Phosphotransferase,Macro-Creatine Kinase,Creatine Phosphotransferase, ATP,Kinase, Creatine,Macro Creatine Kinase,Phosphocreatine Phosphotransferase, ADP,Phosphokinase, Creatine,Phosphotransferase, ADP Phosphocreatine,Phosphotransferase, ATP Creatine
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D012519	Sarcoplasmic Reticulum	A network of tubules and sacs in the cytoplasm of SKELETAL MUSCLE FIBERS that assist with muscle contraction and relaxation by releasing and storing calcium ions.	Reticulum, Sarcoplasmic,Reticulums, Sarcoplasmic,Sarcoplasmic Reticulums
D018482	Muscle, Skeletal	A subtype of striated muscle, attached by TENDONS to the SKELETON. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles.	Anterior Tibial Muscle,Gastrocnemius Muscle,Muscle, Voluntary,Plantaris Muscle,Skeletal Muscle,Soleus Muscle,Muscle, Anterior Tibial,Muscle, Gastrocnemius,Muscle, Plantaris,Muscle, Soleus,Muscles, Skeletal,Muscles, Voluntary,Skeletal Muscles,Tibial Muscle, Anterior,Voluntary Muscle,Voluntary Muscles
D018763	Muscle Fatigue	A state arrived at through prolonged and strong contraction of a muscle. Studies in athletes during prolonged submaximal exercise have shown that muscle fatigue increases in almost direct proportion to the rate of muscle glycogen depletion. Muscle fatigue in short-term maximal exercise is associated with oxygen lack and an increased level of blood and muscle lactic acid, and an accompanying increase in hydrogen-ion concentration in the exercised muscle.	Fatigue, Muscle,Muscular Fatigue,Fatigue, Muscular