[Cumene hydroperoxide changes the type of conductivity of the mitochondrial membrane for K+]

The release of K+ from mitochondria under hypotonic conditions is a non-electrogenic process with an activity maximum at alkaline values of pH. Under these conditions an addition of cumene hydroperoxide causes the appearance of a second K+ release maximum at acidic pH values. The stimulation of K+ release by cumene hydroperoxide is accompanied by a decrease of the transmembrane potential and the accumulation of lipid peroxidation products. The effects of cumene hydroperoxide are prevented by the free radical scavenger, ionol. The acceleration of K+ release is not due to the activation of the non-electrogenic mechanism. It is concluded that the cumene hydroperoxide-induced release of K+ is caused by an increase in the nonspecific ionic permeability of the inner mitochondrial membrane and is controlled by free radical reactions. The contribution of K+ permeability of both types to the hormone-induced changes in the ionic composition of the mitochondrial matrix is discussed.