Uptake and release of 5-hydroxytryptamine by rabbit platelets: I. Thermodynamic studies |
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Affiliation: | 2. Department of Cell Biology, Harvard Medical School, Boston, MA 02115;4. Broad Institute of MIT and Harvard, Cambridge, MA 02142;1. Department of Biology & Institute of Biochemistry, Carleton University, Ottawa, ON, Canada;2. Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, Centre for Infection, Immunity and Inflammation, Ottawa Institute of Systems Biology, Ottawa, ON, Canada;3. Centre for Catalysis Research and Innovation, University of Ottawa, Ottawa, ON, Canada |
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Abstract: | The uptake and release of 5-hydroxytryptamine from rabbit platelets has been investigated at different temperatures. The Km values at 37 and 45° are comparable, while the Vm increases with temperature. A more pronounced enhancement of uptake was produced by glucose at 45 than at 37°. While individual steps of activation may be involved, the overall uptake or release may be treated as a unitary step. The release may depend on two moles of ATP, while the uptake may depend upon three moles, or one additional mole, of ATP. Values for standard free-energy change, temperature coefficient, and energy of activation for these two processes are reported. |
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