Tag Archives: K+ATP-channel

The effect of potential-dependent potassium uptake on membrane potential in rat brain mitochondria

O. V. Akopova, V. I. Nosar, L. I. Kolchinskaya,
I. N. Mankovska, M. K. Malysheva, V. F. Sagach

Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv;
e-mail: luko@biph.kiev.ua

The effect of potential-dependent potassium uptake on the transmembrane potential difference (ΔΨm) in rat brain mitochondria has been studied­. It was shown that in potassium concentration range of 0-120 mM the potential-dependent K+-uptake into matrix leads to the increase in respiration rate and mitochondrial depolarization. ATP-dependent potassium channel (K+ATP-channel) blockers, gliben­clamide and 5-hydroxydecanoate, block ~35% of potential-dependent potassium uptake in the brain mitochondria. It was shown that K+ATP-channel blockage results in membrane repolarization by ~20% of control, which is consistent with experimental dependence of ΔΨm on the rate of potential-dependent potassium uptake. Obtained experimental data give the evidence that functional activity of K+ATP-channel is physiologically important in the regulation of membrane potential and energy-dependent processes in brain mitochondria.

The effect of ATP-dependent K(+)-channel opener on transmembrane potassium exchange and reactive oxygen species production upon the opening of mitochondrial pore

O. V. Akopova, L. I. Kolchinskaya, V. I. Nosar, V. A. Bouryi, I. N. Mankovska, V. F. Sagach

Bogomoletz Institute of Physiology, National Academy of Sciences of Ukraine, Kyiv;
e-mail: a-dubensky@mail.ru

The effect of mitochondrial ATP-dependent K+-channel (K+ATP-channel) opener diazoxide (DZ) on transmembrane potassium exchange and reactive oxygen species (ROS) formation under the opening of mitochondrial permeability transition pore (MPTP) was studied in rat liver mitochondria. The activation of K+-cycling (K+-uptake and K+/H+-exchange) by DZ was established with peak effect at ≤500 nM. It was shown that MPTP opening as well resulted in the activation of K+-cycling together with simultaneous activation of Ca2+-cycle in mitochondria. In the absence of depolarization Ca2+-cycle is supported by MPTP and Ca2+-uniporter. The stimulation of K+/H+-exchange by MPTP opening led to the activation of K+-cycle, but further activation of K+/H+-exchange resulted in MPTP inhibition. Under the same conditions the decrease in mitochondrial ROS production was observed. It was proposed that the decrease in ROS formation together with K++-exchange activation could be the constituents of the complex effect of MPTP inhibition induced by K+ATP-channel opener.

Estimation of ATP-dependent K(+)-channel contribution to potential-dependent potassium uptake in the rat brain mitochondria

O. V. Akopova, V. I. Nosar, L. I. Kolchinskaya, I. N. Mankovska, V. F. Sagach

Bogomoletz Institute of  Physiology, National Academy of Sciences of Ukraine, Kyiv;
e-mail: a-dubensky@mail.ru

The effect of potassium on state 4 respiration (substrate oxidation in the absence of ADP) was investigated. It was shown that potential-dependent potassium uptake in the brain mitochondria results in mitochondrial depolarization. Taking into account depolarization effect of potassium, the contribution of the endo­genous proton leak as well as K+-uptake to the re­spiration rate was calculated. It was shown that such estimation allows the share of ATP-dependent potassium channel contribution to potential-dependent potassium uptake to be determined by polarographic method.