Potassium transport through mitochondrial inner membrane was identified to trigger cytoprotection. This transport is strictly ion channel dependent and is similar to plasma membrane ion channels activity. In the inner mitochondrial membrane were found three different potassium selective ion channels: ATP-regulated potassium (mitoK_ATP) channel, large conductance Ca²⁺-activated potassium (mitoBK_Ca) channel and voltage dependent potassium (mitoKv1.3) channel.

Mitochondrial BK_Ca channel was first found in human glioma cell line LN229. Later its presence was describe also in guinea pig ventricular cells, rat brain and rat skeletal muscle. Activity of this channel depends on mitochondrial membrane potential and calcium ions. This channel is activated by NS1619 and blocked by iberiotoxin, charibdotoxin or paxiline.

Potassium flux caused by opening of the mitoBK_Ca leads to changes in the respiration rate. Therefore respiration changes can indicate if the channel is opened or closed. We have shown that calcium in micromolar concentration range can increase respiration rate in isolated rat skeletal muscle mitochondria. This increase is inhibited by nanomolar concentration of iberiotoxin, but not by cyclosporine A, a known the permeability transition pore inhibitor.

Additional we discuss the possibility of regulation of mitochondrial potassium channels by various protein kinases. There are many observations suggesting modulation of mitochondrial potassium channels by cAMP-dependent protein kinases, different protein kinase C isoforms and protein kinase G. We are focused on establishing the role of mitochondrial potassium channel phosphorylation event in regulation of the channel. Also presence of different PKC isozymes in mitochondria fraction was verified.

Key words: large conductance Ca²⁺-activated potassium channel; calcium; kinases

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