Résumé :
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Communication n° 261. Introduction : Extracellular adenosine triphosphate (ATP) is involved in the regulation of various events such as cell proliferation and muscle contraction. ATP acts through the activation of ionotropic P2X receptors and also through metabotropic P2Y receptors. L-carnitine is necessary for the transfer of fatty acids into mitochondrial matrix where beta-oxidation occurs. L-carnitine is a key molecule in muscle metabolism whose energetics is strictly dependent on fatty acid oxidation. Objective : The objective of this work was to determine the effect of extracellular ATP on L-carnitine metabolism and on the proliferation rate of C2C12 myoblastic cells. Results : In the presence of ATP, C2C12 cells exhibited an increased uptake of L-carnitine. This phenomenon appeared to be dose-dependent. This effect was observed as low as 0.1 µM of ATP and increased as the concentration of ATP increased. In the presence of 1 mM of ATP, the uptake of L-carnitine was multiplied by 10. The rate of proliferation of C2C12 cells was also modified by ATP : in the presence of 1 mM of ATP and after 3 days of treatment, this rate was multiplied by 2.4. The use of antagonists of the P2 receptors shows that these effects are associated with the activation of several subtypes of P2 receptors. Conclusions : ATP is released by muscle cells, particularly during physical exercise. Free ATP found around muscle cells could interact with P2 receptors located on muscle cell membrane. The activation of these cells may induce an increased L-carnitine metabolism leading to an increased lipid metabolism. Concomitantly, ATP induces a higher rate of cell proliferation. Extracellular ATP may act as a signal among muscle cells and modulates cell proliferation.
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