Rates of ATP production and protein synthesis rates were simultaneously studied using the isolated rat brain mitochondria and different types of brain polysomes (total, free, microsomal and mitochondrial membrane-bound). Protein synthesis was measured using a special reticulocyte lysate cell-free incubation medium. Prior to incubation, the intact ("unbroken") mitochondria were pretreated by several xenobiotics and natural metabolic effectors. The mitochondria incubated without these additions were used as controls. Chemically-promoted inhibition of ATP systhesis correlated with a significant activation of protein synthesis directed by the mitochondrial membrane-bound polysomes. The induction of ATP synthesis leads to a marked suppression of mitochondrial translation. Application of the selective translation blockers do not influence the ATP formation inside the isolated mitochondria. In general, mitochondrial membrane-found polysomes isolated from the intact normal organella are least active as compared with other tested polysomal fractions while the releasing of polysomes from mitochondrial membranes by Triton X-100 leads to the essential increase of the activity of these separated translation mechanisms. The separation of polysomes from the microsomal membranes do not change the activity of the former. A possible molecular mechanism, interdependence and biological significance of the established phenomena are discussed.