Steady state regulation of extramitochondrial Ca2+ by rat liver mitochondria: effects of Mg2+ and ATP.
An electrode-based system capable of monitoring ionized Ca2+ concentrations ([Ca2+]) < 1 microM was used to examine the regulation of extramitochondrial [Ca2+] by rat liver mitochondria. At the point of steady state balance between Ca2+ uptake and release, [Ca2+] ranged between 0.5 and 1.0 microM in a KCl/Hepes/succinate medium. When 1 mM Mg2+ was included in this basal medium, the range of steady state [Ca2+] values was 1-2 microM. Further additions (3 mM MgATP and 2 mM Pi) lowered extramitochondrial [Ca2+] to 0.4-0.8 microM. Thus under experimental conditions simulating the control of cytosolic [Ca2+], liver mitochondria buffered extramitochondrial [Ca2+] at constant values within the range of [Ca2+] estimated for liver cytosol; and cytosolic levels of Mg2+ and ATP significantly affected those steady state [Ca2+] values in directions consistent with previously reported effects of those modulators on mitochondrial Ca2+ uptake and release.
D000255:Adenosine Triphosphate / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology*; D008297:Male; D008930:Mitochondria, Liver / Q000378:metabolism*; D051381:Rats
D000255:Adenosine Triphosphate; D008274:Magnesium; D002118:Calcium