Macrocompartmentation of total creatine in cardiomyocytes revisited |
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Authors: | Menin Laure Panchichkina Marina Keriel Christiane Olivares José Braun Urmo Seppert Enn K. Saks Valdur A. |
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Affiliation: | (1) Laboratory of Fundamental and Applied Bioenergetics, Joseph Fourier University, Grenoble, France;(2) Department of Pathophysiology, University of Tartu, Estonia;(3) Laboratory of Bioenergetics, National Institute of Chemical Physics and Biophysics, Tallinn, Estonia |
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Abstract: | Distribution of total creatine (free creatine + phosphocreatine) between two subcellular macrocompartments – mitochondrial matrix space and cytoplasm – in heart and skeletal muscle cells was reinvestigated by using a permeabilized cell technique. Isolated cardiomyocytes were treated with saponin (50 g/ml for 30 min or 600 g/ml for 1 min) to open the outer cellular membrane and release the metabolites from cytoplasm (cytoplasmic fraction, CF). All mitochondrial population in permeabilized cells remained intact: the outer membrane was impermeable for exogenous cytochrome c, the acceptor control index of respiration exceeded 10, the mitochondrial creatine kinase reaction was fully coupled to the adenine nucleotide translocator. Metabolites were released from mitochondrial fraction (MF) by 2–5% Triton X100. Total cellular pool of free creatine + phosphocreatine (69.6 ± 2.1 nmoles per mg of protein) was found exclusively in CF and was practically absent in MF. When fibers were prepared from perfused rat hearts, cellular distribution of creatine was not dependent on functional state of the heart and only slightly modified by ischemia. It is concluded that there is no stable pool of creatine or phosphocreatine in the mitochondrial matrix in the intact muscle cells, and the total creatine pool is localized in only one macrocompartment – cytoplasm. |
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Keywords: | heart skeletal muscle mitochondria creatine phosphocreatine compartmentation |
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