Calcium fluxes into and out of cytosol in human platelets: analysis of experimental data |
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Authors: | Juška Alfonsas |
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Institution: | Vilniaus Gedimino technikos universitetas, Saul?tekio al. 11, 10223 Vilnius, Lithuania |
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Abstract: | The purpose of this research was to analyse experimental data concerning cytosolic calcium concentration in view of the mechanisms involved in calcium fluxes in human platelets. The parameters of model curves are related to the properties of the entities responsible for control or maintenance of cytosolic calcium concentration. It has been shown that: (a) biphasicity of increase in cytosolic calcium concentration caused by inhibition of SERCAs either by TBHQ and TG or by TG alone is related to fast and slow discharge of acidic calcium stores and DTS; (b) biphasicity of decline in cytosolic calcium concentration after its rise caused by stimulation of platelets by the agonists is related to non-synchronous extrusion of calcium by PMCA and NCX; (c) NCX is active only in calcium containing medium: calcium ion(s) are necessary to be bound to the site(s) located on the medium-facing side of the (macro)molecule; (d) PMCA is likely to be activated either by binding calcium ion(s) to the site(s) located on its cytosol-facing side or by unbinding identical ion(s) from the site(s) on its medium-facing side. |
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Keywords: | Abbreviations: NCX calcium&ndash sodium exchanger PMCA plasma membrane calcium ATPase SERCA endomembrane calcium ATPase TG thapsigargin TBHQ 2 5-di-(tert-butyl)-1 4-hydroquinone |
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