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Calcium Uptake in Rat Liver Mitochondria Accompanied by Activation of ATP-Dependent Potassium Channel

O. V. Akopova*, V. I. Nosar, I. N. Mankovskaya, and V. F. Sagach

Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kiev, Ukraine; E-mail: circul@biph.kiev.ua; mankovsk@biph.kiev.ua

* To whom correspondence should be addressed.

Received June 9, 2007; Revision received March 24, 2008
The influence of potassium ions on calcium uptake in rat liver mitochondria is studied. It is shown that an increase in K+ and Ca2+ concentrations in the incubation medium leads to a decrease in calcium uptake in mitochondria together with a simultaneous increase in potassium uptake due to the potential-dependent transport of K+ in the mitochondrial matrix. Both effects are more pronounced in the presence of an ATP-dependent K+-channel (K+ATP-channel) opener, diazoxide (Dz). Activation of the K+ATP-channel by Dz alters the functional state of mitochondria and leads to an increase in the respiration rate in state 2 and a decrease in the oxygen uptake and the rate of ATP synthesis in state 3. The effect of Dz on oxygen consumption in state 3 is mimicked by valinomycin, but it is opposite to that of the classical protonophore uncoupler CCCP. It is concluded that the potential-dependent uptake of potassium is closely coupled to calcium transport and is an important parameter of energy coupling responsible for complex changes in oxygen consumption and Ca2+-transport properties of mitochondria.
KEY WORDS: ATP-dependent K+-channels, mitochondria, potassium, calcium, transport, oxygen consumption, diazoxide

DOI: 10.1134/S000629790810012X