Intramitochondrial K+ as activator of carboxyatractyloside-induced Ca2+ release.
The role of intramitochondrial K+ content on the increase in membrane permeability to Ca2+, as induced by carboxyatractyloside was studied. In mitochondria containing a high K+ concentration (83 nmol/mg), carboxyatractyloside induced a fast and extensive mitochondrial Ca2+ release, membrane de-energization, and swelling. Conversely, in K(+)-depleted mitochondria (11 nmol/mg), carboxyatractyloside was ineffective. The addition of 40 mM K+ to K(+)-depleted mitochondria restored the capability of atractyloside to induce an increase in membrane permeability to Ca2+ release. The determination of matrix free Ca2+ concentration showed that, at an external free-Ca2+ concentration of 0.8 microM, control mitochondria contained 3.9 microM of free Ca2+ whereas K(+)-depleted mitochondria contained 0.9 microM free Ca2+. It is proposed that intramitochondrial K+ affects the matrix free Ca2+ concentration required to induce a state of high membrane permeability.
Chávez
E
E
Departamento de Bioquímica, Ignacio Chávez, México, D.F.
Moreno-Sánchez
R
R
Zazueta
C
C
Reyes-Vivas
H
H
Arteaga
D
D
D000818:Animals; D001278:Atractyloside / Q000031:analogs & derivatives* / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002414:Cations, Monovalent; D007425:Intracellular Membranes / Q000187:drug effects / Q000378:metabolism; D007668:Kidney / Q000378:metabolism*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D008933:Mitochondrial Swelling / Q000187:drug effects; D011188:Potassium / Q000378:metabolism / Q000502:physiology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats
D002414:Cations, Monovalent; D001278:Atractyloside; D011189:Potassium Chloride; D011188:Potassium; C003853:carboxyatractyloside; D002118:Calcium