A re-evaluation of energy-independent calcium-ion binding by rat liver mitochondria.
The impermeability of the mitochondrial inner membrane to the chelator ethanedioxybis(ethylamine)tetra-acetic acid permits discrimination between Ca(2+) which has been transported to the internal (matrix) phase and Ca(2+) which binds to the external surfaces of the mitochondrion. With this technique, it is shown that ;energy-independent high-affinity' binding is a measure of carrier-mediated active Ca(2+) transport in respiration-inhibited mitochondria; the carrier also transports Ca(2+) to the internal phase after treatment with carbonyl cyanide m-chlorophenylhydrazone, but in this case the active-transport component is inhibited. The Ca(2+)-binding sites associated with the external membrane surfaces are similar in concentration and affinity for both inhibited and uncoupled mitochondria; it was not possible to measure external Ca(2+) binding which could be identified as carrier specific. The results are discussed in relation to the mechanism of mitochondrial Ca(2+) transport, and to previous studies of energy-independent Ca(2+) binding.
D000818:Animals; D000968:Antimycin A / Q000494:pharmacology; D001665:Binding Sites; D002118:Calcium / Q000378:metabolism*; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D003992:Dibucaine / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D004735:Energy Transfer; D007700:Kinetics; D007811:Lanthanum / Q000494:pharmacology; D008433:Mathematics; D008566:Membranes / Q000378:metabolism; D008930:Mitochondria, Liver / Q000187:drug effects / Q000378:metabolism*; D008954:Models, Biological; D009840:Oligomycins / Q000494:pharmacology; D051381:Rats; D011955:Receptors, Drug; D012402:Rotenone / Q000494:pharmacology; D012430:Ruthenium Red / Q000494:pharmacology; D013997:Time Factors
D009840:Oligomycins; D011955:Receptors, Drug; D012402:Rotenone; D012430:Ruthenium Red; D004533:Egtazic Acid; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D000968:Antimycin A; D007811:Lanthanum; D003992:Dibucaine; D002118:Calcium