Compartmentation of energy metabolism in atrial myocardium of patients undergoing cardiac surgery |
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Authors: | Evelin Seppet Margus Eimre Nadezhda Peet Kalju Paju Ehte Orlova Mati Ress Sirje Kõvask Andres Piirsoo Valdur A Saks Frank N Gellerich Stephan Zierz Enn K Seppet |
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Institution: | (1) Departments of Pathophysiology, Human Genetics and Biology and Cardiovascular and Thoracic Surgery, Centre of Molecular and Clinical Medicine, Faculty of Medicine, Tartu, Laboratory of Bioenergetics, National Institute of Chemical and Biological Physics, University of Tartu, Tallinn, Estonia;(2) Muskellabor der Neurologischen Klinik der Martin-Luther-Universität Halle-Wittenberg Halle/Saale, Germany;(3) Department of Pathophysiology, Faculty of Medicine, University of Tartu, 19 Ravila Street, 50411 Tartu, Estonia |
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Abstract: | The parameters of oxidative phosphorylation and its interaction with creatine kinase (CK)- and adenylate kinase (AK)-phosphotransfer networks in situ were studied in skinned atrial fibers from 59 patients undergoing coronary artery bypass surgery, valve replacement/correction and atrial septal defect correction. In atria, the mitochondrial CK and AK are effectively coupled to oxidative phosphorylation, the MM-CK is coupled to ATPases and there exists a direct transfer of adenine nucleotides between mitochondria and ATPases. Elimination of cytoplasmic ADP with exogenous pyruvate kinase was not associated with a blockade of the stimulatory effects of creatine and AMP on respiration, neither could it abolish the coupling of MM-CK to ATPases and direct transfer of adenine nucleotides. Thus, atrial energy metabolism is compartmentalized so that mitochondria form functional complexes with adjacent ATPases. These complexes isolate a part of cellular adenine nucleotides from their cytoplasmic pool for participating in energy transfer via CK- and AK-networks, and/or direct exchange. Compared to atria in sinus rhythm, the fibrillating atria were larger and exhibited increased succinate-dependent respiration relative to glutamate-dependent respiration and augmented proton leak. Thus, alterations in mitochondrial oxidative phosphorylation may contribute to pathogenesis of atrial fibrillation. (Mol Cell Biochem 270: 49–61, 2005) |
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Keywords: | skinned fibers human myocardium mitochondria oxidative phosphorylation phosphotransfer networks |
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