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The dynamics of mitochondrial Ca2+ fluxes

AuthorsFuente, Sergio de la; Montenegro, Pablo CSIC; Fonteriz, Rosalba I. CSIC ORCID; Moreno, Alfredo; Lobatón, Carmen D.; Montero, Mayte CSIC ORCID CVN; Álvarez, Javier
KeywordsCa2+ fluxes
Ca2+ dynamics
Ca2+ buffering
Issue DateOct-2010
CitationBBA - Bioenergetics 1797(10): 1727-1735 (2010)
AbstractWe have investigated the kinetics of mitochondrial Ca2+ influx and efflux and their dependence on cytosolic [Ca2+] and [Na+] using low-Ca2+-affinity aequorin. The rate of Ca2+ release from mitochondria increased linearly with mitochondrial [Ca2+] ([Ca2+]M). Na+-dependent Ca2+ release was predominant al low [Ca2+]M but saturated at [Ca2+]M around 400 μM, while Na+-independent Ca2+ release was very slow at [Ca2+]M below 200 μM, and then increased at higher [Ca2+]M, perhaps through the opening of a new pathway. Half-maximal activation of Na+-dependent Ca2+ release occurred at 5–10 mM [Na+], within the physiological range of cytosolic [Na+]. Ca2+ entry rates were comparable in size to Ca2+ exit rates at cytosolic [Ca2+] ([Ca2+]c) below 7 μM, but the rate of uptake was dramatically accelerated at higher [Ca2+]c. As a consequence, the presence of [Na+] considerably reduced the rate of [Ca2+]M increase at [Ca2+]c below 7 μM, but its effect was hardly appreciable at 10 μM [Ca2+]c. Exit rates were more dependent on the temperature than uptake rates, thus making the [Ca2+]M transients to be much more prolonged at lower temperature. Our kinetic data suggest that mitochondria have little high affinity Ca2+ buffering, and comparison of our results with data on total mitochondrial Ca2+ fluxes indicate that the mitochondrial Ca2+ bound/Ca2+ free ratio is around 10- to 100-fold for most of the observed [Ca2+]M range and suggest that massive phosphate precipitation can only occur when [Ca2+]M reaches the millimolar range.
Description9 páginas, 9 figuras.-- El pdf del artículo es la versión revisa de autor.
Publisher version (URL)http://dx.doi.org/10.1016/j.bbabio.2010.06.008
Appears in Collections:(IBGM) Artículos
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