Characterization of Ca2+ transport in Euglena gracilis mitochondria.
The present study was designed to establish the characteristics of the Ca2+ fluxes in isolated mitochondria of the protist Euglena gracilis. Uptake of Ca2+ and Sr2+ was supported by succinate and lactate oxidation. Ca2+ influx was slightly inhibited by 5 microM Ruthenium red and completely blocked by La3+ with a half-maximal inhibition attained at 50 microM. The addition of inorganic phosphate induced a 3-fold stimulation of Ca2+ uptake. Ca2+ uptake was inhibited by Mg2+ only in the absence of phosphate. Ca2+ efflux was induced by Na+, Li+ and K+ through a diltiazem-insensitive reaction. Ca2+ release, collapse of membrane potential and swelling were induced by Hg2+ and Cd2+ but not by carboxyatractyloside; cyclosporin A did not prevent the Ca2+ release induced by the heavy metal ions. Ca2+ uptake was achieved in the presence of 3 microM antimycin or 0.1 mM cyanide; this finding indicates that the alternative respiratory chain present in Euglena mitochondria can support this energy-dependent reaction. The data obtained suggest similar pathways, but different regulatory mechanisms, for Ca2+ transport between protist and mammalian mitochondria.
Uribe
A
A
Departamento de Bioquímica, Instituto Nacional de Cardiología, México D.F., Mexico.
Chávez
E
E
Jiménez
M
M
Zazueta
C
C
Moreno-Sánchez
R
R
D000818:Animals; D001278:Atractyloside / Q000031:analogs & derivatives / Q000494:pharmacology; D001693:Biological Transport, Active / Q000187:drug effects; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D004579:Electron Transport; D005056:Euglena gracilis / Q000378:metabolism / Q000648:ultrastructure*; D017136:Ion Transport / Q000187:drug effects; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D007811:Lanthanum / Q000494:pharmacology; D008094:Lithium / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D008628:Mercury / Q000494:pharmacology; D008928:Mitochondria / Q000378:metabolism*; D010710:Phosphates / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D012430:Ruthenium Red / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D013324:Strontium / Q000378:metabolism; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid
D007773:Lactates; D010710:Phosphates; D013386:Succinates; D002104:Cadmium; D012430:Ruthenium Red; D001278:Atractyloside; D019344:Lactic Acid; D007811:Lanthanum; D008094:Lithium; D012964:Sodium; D019802:Succinic Acid; D008628:Mercury; D008274:Magnesium; D011188:Potassium; C003853:carboxyatractyloside; D002118:Calcium; D013324:Strontium