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Mitochondria from mammalian tissues possess an elaborate system for 2+ 2+ transporting Ca across their inner membrane which consists of Ca import, 2+ via the Ca uniporter, in response to the mitochondrial membrane 2+ + potential ?? and of Ca release by an antiport system in exchange for H + 9,23 or Na (see Fig. l) . Because the uniporter is dependent upon the external 2+ 2+ 2+ 2+ Ca concentration ([Ca ]), mitochondria accumulate Ca until the [Ca ] o o 2+ decreases to the level at which the uniporter activity balances the Ca efflux. 2+ The [Ca ] at which the uniporter and efflux activities are equal is defined o the “setpoint” andcorresponds to values between 0.3-3µM. 2+ Figure 1. The Ca transport system of the inner membrane of mammalian mitochondria. U, + 2+ + + uniporter. I, Na -independent efflux mechanism or Ca /2H exchanger. D, Na -dependent 2+ + efflux mechanism or Ca /2Na exchanger. PTP, permeability transition pore. FP, 11 flavoprotein. ?? membrane potential. ? pH gradient. Adapted from .
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NEW TRENDS IN QUANTUM SYSTEMS IN CHEMISTRY AND PHYSICS Progress in Theoretical Chemistry and Physics - VOLUME 7 - Honorary Editors: W. N. Lipscomb (Harvard University, Cambridge, MA, U. S. A.) I. Prigogine (Université Libre de Bruxelles, Belgium) Editors-in-Chief: J. Maruani (Laboratoire de Chimie Physique, Paris, France) S. Wilson (Rutherford Appleton Laboratory, Oxfordshire, United Kingdom) Editorial Board: H. Ågren (Royal Institute of Technology, Stockholm, Sweden) D. Avnir (Hebrew University of Jerusalem, Israel) J. Cioslowski (Florida State University, Tallahassee, FL, U.S.A.) R. Daudel (European Academy of Sciences, Paris, France) E.K.U. Gross (Universität Würzburg Am Hubland, Germany) W.F. van Gunsteren (ETH-Zentrum, Zürich, Switzerland) K. Hirao (University of Tokyo, Japan) I. Hubac (Komen