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Journal archive > 2007 > N 1 January-February

PROTON TRANSPORT IS NECESSARY FOR DIVALENT METAL CATIONS RELEASE
FROM DEENERGIZED MITOCHONDRIA

O. V. Akopova, V. F. Sagach

Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv;
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The release of divalent cations (Ca2+ and Sr2+) from rat liver mitochondria after membrane depolarization with protonophore (carbonyl cyanide m-chlorophenyl hydrazone, CCCP), sodium azide and K+-ionophore (valinomycin) was studied. It is stated that membrane depolarization itself is not sufficient for cations release from mitochondrial matrix (provided that mitochondrial permeability transition pore is blocked by cyclosporin?A). Complete delivering of divalent cations­ is observed only after protonophore (CCCP) addition to suspension of deenergized mitochondria. The data show that membrane permeabilisation to hydrogen ions (H+) is necessary for complete cation release from the mitochondrial matrix. The enhancement in K+-conductivity of mitochondrial membrane (by valinomycin), on the contrary, is not able to provide complete delivering of cations from mitochondria. It is shown that quantity of divalent metal cation­ released from mitochondria (depolarized and permeabilized for K+ as well) is proportional to the concentration of protonophore (but not K+-ionophore) introduced in the incubation medium. The data obtained lead to the conclusion that H+-permeabilization of the mitochondrial membrane is necessary for the complete release of Са2+ and Sr2+ from mitochondria after membrane depolarization. The possible mechanism of divalent metal cations release from deenergized mitochondria is discussed.

Key words: mitochondria, divalent metals­, calcium, strontium, Ca2+-uniporter, transport, membrane depolarization.

The original article in Russian is available for download in PDF format.

© The Ukrainian Biochemical Journal