Influence of ATP-Dependent K⁺-Channel Opener on K⁺-Cycle and Oxygen Consumption in Rat Liver Mitochondria

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

Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, ul. Bogomoltsa 4, 01601 Kiev, Ukraine; E-mail: a-dubensky@mail.ru; mankovsk@biph.kiev.ua

^* To whom correspondence should be addressed.

Received November 11, 2009; Revision received April 26, 2010

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The influence of the K⁺_ATP-channel opener diazoxide on the K⁺ cycle and oxygen consumption has been studied in rat liver mitochondria. It was found that diazoxide activates the K⁺_ATP-channel in the range of nanomolar concentrations (50-300 nM, K_1/2 ~ 140 nM), which results in activation of K⁺/H⁺ exchange in mitochondria. The latter, in turn, accelerates mitochondrial respiration in respiratory state 2. The contribution of K⁺_ATP-channel to the mitochondrial potassium cycle was estimated using the selective K⁺_ATP-channel blocker glibenclamide. The data show that the relative contribution of K⁺_ATP-channel in the potassium cycle of mitochondria is variable and increases only with the decrease in the ATP-independent component of K⁺ uptake. Possible mechanisms underlying the observed phenomena are discussed. The experimental results more fully elucidate the role of K⁺_ATP-channel in the regulation of mitochondrial functions, especially under pathological conditions accompanied by impairment of the mitochondrial energy state.

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KEY WORDS: ATP-dependent K⁺-channel, mitochondria, potassium, transport, diazoxide, oxygen consumption, potassium cycle

DOI: 10.1134/S0006297910090075

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