title: The stoichiometry of the exchange catalysed by the mitochondrial calcium/sodium antiporter.
abstract: Rat heart mitochondria respiring on succinate in the presence of Ruthenium Red (to inhibit uptake on the Ca2+ uniporter) released Ca2+ on the calcium/sodium antiporter until a steady state was reached. Addition of the ionophore A23187 (which catalyses Ca2+/2H+ exchange) did not perturb this steady state. Thermodynamic analysis showed that if a Ca2+/nNa+ exchange with any value of n other than 2 was at equilibrium, addition of A23187 would cause an obvious change in extramitochondrial free [Ca2+]. Therefore the endogenous calcium/sodium antiporter of mitochondria catalyses electroneutral Ca2+/2Na+ exchange.
mesh_terms: D000818:Animals; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008565:Membrane Proteins / Q000378:metabolism*; D008744:Methylamines / Q000378:metabolism; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism*; D009861:Onium Compounds / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger; D013816:Thermodynamics; D014320:Triphenylmethyl Compounds / Q000378:metabolism
chemical_list: D002352:Carrier Proteins; D008565:Membrane Proteins; D008744:Methylamines; D009861:Onium Compounds; D019831:Sodium-Calcium Exchanger; D014320:Triphenylmethyl Compounds; C011561:triphenylmethylphosphonium; D000001:Calcimycin; D012964:Sodium; C027451:methylamine; D002118:Calcium