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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 0.3-3M. 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 .
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 0.3-3M. 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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