title: The cycling of calcium, sodium, and protons across the inner membrane of cardiac mitochondria.
abstract: A method is described that permits simultaneous determination of the net charge transfer associated with Ca2+ transport by the ruthenium-red-sensitive carrier and the ionized internal [Ca2+] in heart mitochondria. The data indicate that this carrier catalyses a charge-uncompensated flux of Ca2+. Full charge compensation for Ca2+ influx is provided by the respiration-dependent efflux of H+. The net efflux of Ca2+ induced by Na+ is analysed in terms of two other carriers, a Na+-Ca2+ antiporter and a Na+-H+ antiporter. Evidence is presented that these two carriers are separate and that the Na+-H+ exchange is the more rapid. The fluxes of Ca2+, Na+ and H+ during the Na+-induced efflux of Ca2+ support a series of events in which the Na+-H+ exchange enables unidirectional Ca2+ fluxes via the uniport and antiport systems to be integrated into a cycle.
mesh_terms: D000818:Animals; D001692:Biological Transport; D001693:Biological Transport, Active; D002118:Calcium / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000378:metabolism*; D010101:Oxygen Consumption; D051381:Rats; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*; D013386:Succinates / Q000378:metabolism; D013816:Thermodynamics
chemical_list: D013386:Succinates; D012964:Sodium; D012413:Rubidium; D002118:Calcium