Ba2+ ions inhibit the release of Ca2+ ions from rat liver mitochondria.
The release of Ca2+ from respiring rat liver mitochondria following the addition of either ruthenium red or an uncoupler was measured by a Ca2+-selective electrode or by 45Ca2+ technique. Ba2+ ions are asymmetric inhibitors of both Ca2+ release processes. Ba2+ ions in a concentration of 75 microM inhibited the ruthenium red and the uncoupler induced Ca2+ release by 80% and 50%, respectively. For the inhibition, it was necessary that Ba2+ ions entered the matrix space: Ba2+ ions did not cause any inhibition of Ca2+ release if addition of either ruthenium red or the uncoupler preceded that of Ba2+. The time required for the development of the inhibition of the Ca2+ release and the time course of 140Ba2+ uptake ran in parallel. Ba2+ accumulation is mediated through the Ca2+ uniporter as 140Ba2+ uptake was competitively inhibited by extramitochondrial Ca2+ and prevented by ruthenium red. Due to the inhibition of the ruthenium red insensitive Ca2+ release, Ba2+ shifted the steady-state extramitochondrial Ca2+ concentration to a lower value. Ba2+ is potentially a useful tool to study mitochondrial Ca2+ transport.
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D000818:Animals; D001464:Barium / Q000378:metabolism / Q000494:pharmacology*; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D007425:Intracellular Membranes / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008930:Mitochondria, Liver / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D012430:Ruthenium Red / Q000494:pharmacology; D014475:Uncoupling Agents / Q000494:pharmacology
D014475:Uncoupling Agents; D012430:Ruthenium Red; D001464:Barium; D002118:Calcium