Monovalent cations and mitochondrial ATPase activity

The effect of monovalent cations on the ATPase activity of rat liver mitochondria was studied.It was found that alkali-metal ions can activate ATPase when mitochondria become permeable to them by treatment with surface-active agents such as Triton-X-100, alcohols, valinomycin, gramicidin, 2,4-dinitrophenol.The alteration of mitochondrial permeability produced by progressive acidification of the incubation medium indicates that the ability of alkali-metal ions to penetrate mitochondria increases in the order: Li+, Na+, K+, Rb+, and Cs+, which is the order of the decreasing hydrated ionic radii.The results obtained in the presence of valinomycin or gramicidin were comparable with those reported by other workers for the exchange cation–H+. A Na+-activated ATPase could be observed in the presence of high concentrations of valinomycin.The action of surface-active agents on ATPase activity was dependent upon the presence of monovalent cations.It is concluded that control of the metabolism of mitochondria can be exerted through changes in their permeability to cations present in the extramitochondrial cytoplasm.