Mitochondria from rat uterine smooth muscle possess ATP-sensitive potassium channel

The objective of this study was to detect ATP-sensitive K⁺ uptake in rat uterine smooth muscle mitochondria and to determine possible effects of its activation on mitochondrial physiology. By means of fluorescent technique with usage of K⁺-sensitive fluorescent probe PBFI (potassium-binding benzofuran isophthalate) we showed that accumulation of K ions in isolated mitochondria from rat myometrium is sensitive to effectors of K_ATP-channel (ATP-sensitive K⁺-channel) - ATP, diazoxide, glibenclamide and 5HD (5-hydroxydecanoate). Our data demonstrates that K⁺ uptake in isolated myometrium mitochondria results in a slight decrease in membrane potential, enhancement of generation of ROS (reactive oxygen species) and mitochondrial swelling. Particularly, the addition of ATP into incubation medium led to a decrease in mitochondrial swelling and ROS production, and an increase in membrane potential. These effects were eliminated by diazoxide. If blockers of K_ATP-channel were added along with diazoxide, the effects of diazoxide were removed. So, we postulate the existence of K_ATP-channels in rat uterus mitochondria and assume that their functioning may regulate physiological conditions of mitochondria, such as matrix volume, ROS generation and polarization of mitochondrial membrane.