The energy-state of mitochondria during the transport of Ca2+.
The fluctuations of the membrane potential during mitochondrial Ca2+ transport have been monitored with an electrode sensitive to tetraphenylphosphonium. The following conclusions have been reached. 1. The membrane becomes depolarized during the influx of Ca2+. When the bulk of the Ca2+ pulse has been taken up, it repolarizes, but not completely. 2. If all of the accumulated Ca2+ is released from mitochondria and cycling is inhibited, the membrane repolarizes completely. 3. The accumulation of Ca2+ alone does not induce mitochondrial damage. In the presence of inorganic phosphate, the uptake of Ca2+ may lead to complete and irreversible depolarization, depending on the amount of Ca2+ and phosphate accumulated. The irreversible damage observed in the presence of phosphate is prevented by Mg2+.
D000818:Animals; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D008274:Magnesium / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects; D008930:Mitochondria, Liver / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology; D051381:Rats
D010710:Phosphates; D008274:Magnesium; D002118:Calcium