CUPROUS IONS ACTIVATE GLIBENCLAMIDE-SENSITIVE POTASSIUM CHANNEL IN LIVER-MITOCHONDRIA

Cuprous ions at micromolar concentrations induced swelling of mt liver mitochondria in isotonic solutions of potassium thiocyanate and potas sium acetate. The swelling in K-acetate in the presence of the protono phere 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, isoton ic sucrose or choline chloride, but not in NaCl, Cu+ induced a transie nt potassium gradient potential. These results indicate that cuprous i ons at low concentrations, apart from promoting the electroneutral K+/ H+ exchange, facilitate the uniport of K+, presumably by activating th e mitochondrial potassium channel sensitive to glibenclamide. (C) 1996 Academic Press, Inc.