Cuprous ions activate glibenclamide-sensitive potassium channel in liver mitochondria

Cuprous ions at micromolar concentrations induced swelling of rat liver mitochondria in isotonic solutions of potassium thiocyanate and potassium acetate. The swelling in K-acetate in the presence of the protonophore [corrected] carbonyl cyanide m-chloropenylhydrazone was partly inhibited by glibenclamide. In K(+)-containing media, Cu+ collapsed the mitochondrial membrane potential formed by operation of the respiratory chain with succinate or tetramethyl p-phenylenediamine + ascorbate as substrates or by the proton-pumping ATPase. In contrast, in K(+)-free media, isotonic sucrose or choline chloride, but not in NaC1, Cu+ induced a transient potassium gradient potential. These results indicate that cuprous ions at low concentrations, apart from promoting the electroneutral K+/H+ exchange, facilitate the uniport of K+, presumably by activating the mitochondrial potassium channel sensitive to glibenclamide.