Functional complexes of mitochondria with Ca,MgATPases of myofibrils and sarcoplasmic reticulum in muscle cells.

Enn Seppet 1 Tuuli Käämbre 2 Peeter Sikk 2 Toomas Tiivel 2 Heiki Vija 2 Michael Tonkonogi 3 Kent Sahlin 3 Laurence Kay 4 Florence Appaix 4 Urmo Braun 1 Margus Eimre 1 Valdur Saks 2
1 Department of Pathophysiology
2 Laboratory of Bioenergetics
3 Department of Physiology and Pharmacology
4 Bioénergétique fondamentale et appliquée
Abstract : Regulation of mitochondrial respiration in situ in the muscle cells was studied by using fully permeabilized muscle fibers and cardiomyocytes. The results show that the kinetics of regulation of mitochondrial respiration in situ by exogenous ADP are very different from the kinetics of its regulation by endogenous ADP. In cardiac and m. soleus fibers apparent K(m) for exogenous ADP in regulation of respiration was equal to 300-400 microM. However, when ADP production was initiated by intracellular ATPase reactions, the ADP concentration in the medium leveled off at about 40 microM when about 70% of maximal rate of respiration was achieved. Respiration rate maintained by intracellular ATPases was suppressed about 20-30% during exogenous trapping of ADP with excess pyruvate kinase (PK, 20 IU/ml) and phosphoenolpyruvate (PEP, 5 mM). ADP flux via the external PK+PEP system was decreased by half by activation of mitochondrial oxidative phosphorylation. Creatine (20 mM) further activated the respiration in the presence of PK+PEP. It is concluded that in oxidative muscle cells mitochondria behave as if they were incorporated into functional complexes with adjacent ADP producing systems - with the MgATPases in myofibrils and Ca,MgATPases of sarcoplasmic reticulum.
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Biochimica et Biophysica Acta - Molecular Cell Research, Elsevier, 2001, 1504 (2-3), pp.379-95
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Soumis le : mercredi 3 juin 2009 - 12:33:18
Dernière modification le : mardi 3 juillet 2018 - 09:34:10

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Enn Seppet, Tuuli Käämbre, Peeter Sikk, Toomas Tiivel, Heiki Vija, et al.. Functional complexes of mitochondria with Ca,MgATPases of myofibrils and sarcoplasmic reticulum in muscle cells.. Biochimica et Biophysica Acta - Molecular Cell Research, Elsevier, 2001, 1504 (2-3), pp.379-95. 〈inserm-00391063〉

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