[Specific binding of 3',5'-AMP by rat liver mitochondria].

It was found that 3':5'-AMP is bound by rat liver mitochondria with an affinity which corresponds to a physiological concentration of the nucleotide and a low capacity. The bound 3':5'-AMP rapidly dissociates upon dilution of mitochondrial suspensions. This finding points to the existence in mitochondria of a 3':5'-AMP receptor protein.

[Activation of succinate oxidase in the inner membrane of rat liver mitochondria].

It is shown that the process of activation of succinate oxidase from inner membranes of the rat liver mitochondria by succinate and malonate is specific for the succinate dehydrogenase component of oxidase. These activation constants are comparable with those found by other authors in activation of succinate dehydrogenase and succinate oxidase from oxaloacetate-preincubated submitochondrial fragments of the bull heart. Probably, the 4-fold activation of succinate oxidase from inner membranes of the liver mitochondria reported in this paper depends on separation of endogenous oxaloacetate from the succinate dehydrogenase component of oxidase.

[Submitochondrial distribution of cAMP during incubation with rat liver mitochondria].

Labeled cAMP incubated with rat liver mitochondria penetrates not only through outer mitochondrial membranes, but also into mitoplasts, where it is accumulated mainly in the matrix. Damage of mitochondrial membranes caused by single freezing-thawing treatment promotes no influx, but efflux of cAMP from mitoplasts. cAMP molecules penetrate inside mitochondria largely in an unchanged state in all submitochondrial fractions, as was demonstrated by the TLC method.

[Study of mitochondrial permeability for labeled cAMP].

Incubation of rat liver mitochondria with 3H-and 14C-cAMP under the conditions which are conducive to the activation of mitochondrial respiration by cAMP resulted in the penetration of cAMP into the mitochondria. Subfractionation of mitochondria was made with the use of digitonin and 0.1% Triton X-100.