M. V. Rudnytska, H. V. Danylovych*, M. R. Pavliuk, Yu. V. Danylovych

Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
*e-mail: danylovychanna@ukr.net

Received: 17 July 2025; Revised: 25 September 2025;
Accepted: 28 November 2025; Available on-line:    2025

Potassium ions affect Ca²⁺ transport in mitochondria, the magnitude of the electric potential on the inner mitochondrial membrane, metabolic processes in the matrix, and osmoregulation. The aim of this study was to identify different subtypes of K⁺ channels in the mitochondria of rat myometrium. Isolated mitochondria were obtained from the myometrium of non-pregnant Wistar rats by differential centrifugation. Potassium ion accumulation was studied by spectrofluorimetry using the K⁺-sensitive fluorescent probe PBFI-AM. Myometrial mitochondria effectively accumulate potassium ions within the concentration range of 25–150 mM. No increase in PBFI fluorescence was observed when K⁺ ions were replaced by choline in equimolar concentrations. In the presence of voltage-operated K⁺ channels inhibitor 4-aminopyridine, Ca²⁺-dependent K⁺ channels blockers charybdotoxin or paxilline, mitoK_ATP channels inhibitors glibenclamide, 5-hydroxydecanoic acid, or 200 μM ATP, a significant decrease in the PBFI fluorescence signal was observed. Conversely, application of Ca²⁺-dependent K⁺ channels specific activators NS11021 and NS1619, as well as of mitoK_ATP-specific activator cromakalim, resulted in increased mitochondrial K⁺ accumulation. The efficiency of K⁺ uptake increased further with the addition of 25–100 μM Ca²⁺ in the presence of 4-aminopyridine and ATP. The results obtained indicate the presence of voltage-operated and Ca²⁺-dependent subtypes of K⁺ channels, as well as of H⁺/K⁺ exchange system in myometrial mitochondria in addition to mitoK_ATP channels.

Keywords: calcium, K+ channels modulators, mitochondria, potassium ions accumulation, rat myometrium