Document Detail

Contraction-mediated glycogenolysis in mouse skeletal muscle lacking creatine kinase: the role of phosphorylase b activation.
MedLine Citation:
PMID:  12963789     Owner:  NLM     Status:  MEDLINE    
Skeletal muscle that is deficient in creatine kinase (CK-/-) exhibits accelerated glycogenolysis during contraction. Understanding this phenomenon could provide insight into the control of glycogenolysis during contraction. Therefore, glycogen breakdown was investigated in isolated extensor digitorum longus CK-/- muscle. Muscles were stimulated to produce repeated tetani for 20 s in the presence of sodium cyanide to block mitochondrial respiration. Accumulation of lactate after stimulation was similar in wild-type (WT) and CK-/- muscles, whereas accumulation of glucose-6-phosphate was twofold higher in CK-/- muscles, indicating greater glycogenolysis in CK-/- muscles. Total phosphorylase activity was decreased by almost 30 % in CK-/- muscle (P < 0.001). Phosphorylase fractional activity (-/+ 3.3 mM AMP) was similar in both groups in the basal state (about 10 %), but increased to a smaller extent in CK-/- muscles after stimulation (39 +/- 4 % vs. 52 +/- 4 % in WT, P < 0.05). Inorganic phosphate, the substrate for phosphorylase, increased marginally in CK-/- muscles after stimulation (basal = 25.3 +/- 2.2 micromol (g dry muscle)-1; stimulated = 33.9 +/- 2.3 micromol (g dry muscle)-1), but substantially in WT muscles (basal = 11.4 +/- 0.7 micromol (g dry muscle)-1; stimulated = 54.2 +/- 4.5 micromol (g dry muscle)-1). Kinetic studies of phosphorylase b (dephosphorylated enzyme) from muscle extracts in vitro demonstrated higher relative activities in CK-/- muscles (60-135 %) in response to low AMP concentrations (up to 50 microM) in both the basal state and after stimulation (P < 0.05), whereas no differences in activity between CK-/- and WT muscles were observed at high AMP concentrations (> 100 microM). These data indicate that allosteric activation of phosphorylase b accounts for the accelerated glycogenolysis in CK-/- muscle during contraction.
Abram Katz; Daniel C Andersson; Josephine Yu; Barbara Norman; Marie E Sandstrom; Be Wieringa; Hakan Westerblad
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Publication Detail:
Type:  In Vitro; Journal Article; Research Support, Non-U.S. Gov't     Date:  2003-09-08
Journal Detail:
Title:  The Journal of physiology     Volume:  553     ISSN:  0022-3751     ISO Abbreviation:  J. Physiol. (Lond.)     Publication Date:  2003 Dec 
Date Detail:
Created Date:  2003-12-03     Completed Date:  2004-09-23     Revised Date:  2013-06-09    
Medline Journal Info:
Nlm Unique ID:  0266262     Medline TA:  J Physiol     Country:  England    
Other Details:
Languages:  eng     Pagination:  523-31     Citation Subset:  IM    
Department of Physiology and Pharmacology, Karolinska Institutet, 17177 Stockholm, Sweden.
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MeSH Terms
Adenosine Diphosphate / metabolism
Adenosine Monophosphate / metabolism,  pharmacology
Adenosine Triphosphate / metabolism
Creatine / metabolism
Creatine Kinase / genetics*
Electric Stimulation
Enzyme Activation / drug effects
Glucose-6-Phosphate / metabolism
Glycogen / metabolism*
Glycogen Phosphorylase / metabolism
Glycogen Synthase / metabolism
Inosine / metabolism
Inosine Monophosphate / metabolism
Lactic Acid / metabolism
Mice, Inbred C57BL
Mice, Knockout
Muscle Contraction / physiology*
Muscle Fatigue / physiology
Muscle, Skeletal / metabolism*
Phosphocreatine / metabolism
Phosphorylase a / metabolism
Phosphorylase b / metabolism*
Sodium Cyanide / pharmacology
Reg. No./Substance:
131-99-7/Inosine Monophosphate; 143-33-9/Sodium Cyanide; 50-21-5/Lactic Acid; 56-65-5/Adenosine Triphosphate; 56-73-5/Glucose-6-Phosphate; 57-00-1/Creatine; 58-63-9/Inosine; 58-64-0/Adenosine Diphosphate; 61-19-8/Adenosine Monophosphate; 67-07-2/Phosphocreatine; 9005-79-2/Glycogen; EC 2.4.1.-/Glycogen Phosphorylase; EC 2.4.1.-/Phosphorylase a; EC 2.4.1.-/Phosphorylase b; EC Synthase; EC Kinase

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