Calcium uptake in rat liver mitochondria accompanied by activation of ATP-dependent potassium channel
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The influence of potassium ions on calcium uptake in rat liver mitochondria is studied. It is shown that an increase in K+ and Ca2+ concentrations in the incubation medium leads to a decrease in calcium uptake in mitochondria together with a simultaneous increase in potassium uptake due to the potential-dependent transport of K+ in the mito-chondrial matrix. Both effects are more pronounced in the presence of an ATP-dependent K+-channel (K ATP + -channel) opener, diazoxide (Dz). Activation of the K ATP + -channel by Dz alters the functional state of mitochondria and leads to an increase in the respiration rate in state 2 and a decrease in the oxygen uptake and the rate of ATP synthesis in state 3. The effect of Dz on oxygen consumption in state 3 is mimicked by valinomycin, but it is opposite to that of the classical protonophore uncoupler CCCP. It is concluded that the potential-dependent uptake of potassium is closely coupled to calcium transport and is an important parameter of energy coupling responsible for complex changes in oxygen consumption and Ca2+-transport properties of mitochondria.
Key wordsATP-dependent K+-channels mitochondria potassium calcium transport oxygen consumption diazoxide
carbonyl cyanide m-chlorophenylhydra-zone
reactive oxygen species
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