Relationship between cAMP and Ca2+ fluxes in human platelet membranes |
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| Authors: | J Enouf R Bredoux N Bourdeau F Giraud C Le Peuch M Lebret S Levy-Toledano |
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| Affiliation: | 1. Unité de Recherches sur la Thrombose expérimentale et l''Hémostase, INSERM U150, CNRS UA334, Hôpital Lariboisière, 6, rue Guy-Patin, F-75475 Paris Cedex 10, France;2. Physiologie de la Nutrition CNRS UA646, Université Paris-Sud, 91405 Orsay Cedex, France;3. INSERM U249, BP 5051, 34033 Montpellier Cedex, France;1. College of Resources and Environment, Northeast Agricultural University, Harbin 150030, Heilongjiang, PR China;2. College of Science, China Agricultural University, Beijing 100083, PR China;1. Department of Electrical Engineering, Bahria University, 13-National Stadium Road, Karachi, 75620, Pakistan;2. Department of Electrical and Power Engineering, Pakistan Navy Engineering College, National University of Science and Technology, Karachi, Pakistan;1. Hamburg University of Technology, Institute of Thermal Separation Processes, Eißendorfer Straße 38, D-21073 Hamburg, Germany;2. Strategic Science Consult SSC Ltd., Beim Alten Gaswerk 5, 22761 Hamburg, Germany |
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| Abstract: | The effect of cAMP (which involved a 23 kDa protein phosphorylation) has been studied on the Ca2+ uptake and Ca2+ release from a human platelet membrane vesicle fraction. It was tested in the presence of the catalytic subunit of the cAMP-dependent protein kinase (C Sub). The addition of C Sub increased the steady state level of the Ca2+ uptake into the membrane vesicles. The effect was enhanced when tested in the absence of Ca2+ precipitating agent. The response was proportional to the dose of C Sub. Moreover, the effect varied with the Ca2+ concentration. The effect of C Sub has been tested on the inositol 1,4,5-trisphosphate (IP3)-induced Ca2+ release. A phosphorylated state of the 23 kDa protein appeared to be necessary. Indeed, a phosphorylation inhibition prevented the IP3 effect and the addition of C Sub increased the percentage of released Ca2+ (without modification of the time course). However, the C Sub dose-dependent response was not linear. The effect of cAMP on the two functions (Ca2+ uptake and Ca2+ release) appears to be different. Therefore, these results led us to suggest a more complex role of cAMP in the regulation of platelet Ca2+ concentration. |
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